types of waves presentation

Chapter 12 Waves

Types of Waves

Longitudinal Waves

Transverse Waves

Surface Waves

Transmission of Waves

Superposition Principle

Interference

Diffraction

Standing Waves & Resonance

Waves & Information

Marvin the Martian would like to send a message from Mars to Earth. There are two ways of sending a message. He could enclose the message in a rocket and physically send it to Earth. Or, he could send some type of signal, maybe in the form of radio waves.

Information can be sent via matter or waves. If sent via waves, nothing material is actually transmitted from sender to receiver. If �you talk to a friend, be it in �person or on the phone, you are �transmitting information via �waves. Nothing is physically �transported from you to your �friend. This would not be the �case, however, if you sent him �a letter.

Waves & Energy

Suppose Charlie Brown wants to wake up Snoopy. Some energy is required to rouse Snoopy from his slumber. Like information, energy can also be transmitted via physical objects or waves. Charlie Brown can transmit energy from himself to Snoopy via Woodstock: Woodstock flies over; his kinetic energy is physically transported in the form a little, yellow bird. Alternatively, Charlie Brown could send a pulse down a rope that’s attached to Snoopy’s dog house. The rope itself is not transported, but the pulse and its energy are!

A mechanical wave is just a disturbance that propagate through a medium. The medium could be air, water, a spring, the Earth, or even people. A medium is any material through which a wave travels. Mechanical wave examples: sound; water waves; a pulse traveling on a spring; earthquakes; a “people wave” in a football stadium.

An electromagnetic wave is simply light of a visible or invisible wavelength. Oscillating intertwined electric and magnetic fields comprise light. Light can travel without medium—super, duper fast.

A matter wave is a term used to describe particles like electrons that display wavelike properties. It is an important concept in quantum mechanics.

A gravity wave is a ripple in the “fabric of spacetime” itself. They are predicted by Einstein’s theroy of relativity, but they’re very difficult to detect.

Mechanical Waves: Three Types

Mechanical waves require a physical medium. The particles in the medium can move in two different ways: either perpendicual or parallel to direction of the wave itself.

In a longitudinal wave, the particles in the medium move parallel to the direction of the wave.

In a transverse wave, the particles in the medium move perpen-dicular to the direction of the wave.

A surface wave is often a combination of the two. Particles typically move in circular or elliptical paths at the surface of a medium.

Longitudinal ↔ Parallel

Transverse ↔ Perpendicular

Surface ↔ Combo

A whole bunch of kids are waiting in line to get their picture taken with Godzilla. The bully in back pushes the kid in front of him, who bumps into the next kid, and so on down the line. A longitudinal pulse is sent through the line of kids. It’s longitudinal because as each kid gets bumped, he moves forwards, then backwards (red arrow), parallel to the direction of the pulse. The location of the pulse is the point where two kids are being compressed together. The next slide shows how the pulse progresses �through the line.

pulse direction

Longitinal Waves (cont.)

C = Compression (high kid density)

R = Rarefaction (low kid density)

The compression (the pulse) moves up the line, but each kid keeps his place in line.

I hope Godzilla eats that bully!

Sound is a Longitudinal Wave

As sound travels through air, water, a solid, etc., the molecules of the medium move back and forth in the direction of the wave, just like the kids in the last example, except the molecules continually move back and forth for as long as the sound persists. If the bully kept shoving the kid in front of

him, a series of pulses would be generated. If he shoved with equal force each time and did this at a regular rate, we would call these pulses a wave. Similarly, when a speaker or a tuning fork vibrates, it repeatedly shoves the air in front of it, and a longitudinal wave propagates through to the air. The speaker shoves air molecules; the bully shoves people. In either case, the components of the medium must bump into their neighbors.

After a great performance at a drum and bugle corps contest, the audience decides to start a wave in the stands. Each person rises and sits at just the right time so the effect is similar to the pulse in Charlie Brown’s rope. Like the Godzilla example, people make up the wave medium here. But this is a transverse wave because, as the wave moves across the stands, folks are moving up and down.

wave direction

Transverse Waves (cont.)

In a transverse wave, molecules aren’t being compressed and spread out as they are in a longitudinal wave. The reason a transverse wave can propagate is because of the attraction between adjacent molecules. Imagine if each person in the stands on the last slide were connected to the person on his left and right with giant rubber bands. As soon the person on one end stood up, the band stretches. The tension in the band pulls his neighbor up, who, in turn, lifts the next guy.

The tension in the rubber bands is analogous to the forces connecting particles of the medium to their neighbors. The colored sections of rope tug on each other as the waves travels through them. If they didn’t, it would be as if the rope were cut, and no wave could travel through it.

Below the surface fluids can typically only transmit longitudinal waves, since the attraction between neighboring molecules is not as strong as in a fluid. At the surface of a lake, water molecules (white dots) move in circular paths, which are partly longitudinal and partly transverse. The molecules are offset, though: when one is at the top of the circle, the one in front of it is near the top. As in any wave, the particles of the medium do not move along with the wave. The water molecules complete a circle each time a crest passes by. Animation

Breaking Waves

Waves break near the shore because the water becomes shallow. Close to the shore the ground beneath the water interferes with the circular motions of the water molecules as they participate in a passing wave. Sandbars further off shore can have the same effect, much to the delight of surfing enthusiasts like Bart.

Seismic Waves

Seismic waves use Earth itself as their medium. Earthquakes produce them and so does a nation when it carries out an underground nuclear test. (Other countries can detect them.) Seismic waves can be longitudinal, transverse, or surface waves. P and S type waves are called body waves, since they are not confined to the surface. Rayleigh waves do most of the shaking during a quake.

“Mini Seismic” Waves

Though we might not refer to them as seismic, anything moving on the ground can transmit waves through the ground. If you stand near a moving locomotive or a heard of charging elephants, you would feel these vibrations. Even something as small as a

beetle generates pulses when it moves. These pulses can be detected by a nocturnal sand scorpion. Sensors on its eight legs can detect both longitudinal and surface waves. The scorpion can determine the direction of the waves based on which legs feel the waves first. It can determine the distance of the prey based on the time delay between the fast moving longitudinal waves and the slower moving surface waves. The greater the time delay, the farther away the beetle. This is the same way seismologists determine the distance of a quake’s epicenter. Sand is not the best conductor of waves, so the scorpion will only be able to detect beetles within about a half meter.

Wave Characteristics

Amplitude (A) – Maximum displacement of particle of the medium from its equilibrium point. The bigger the amplitude, the more energy the wave carries.

Wavelength (λ) – Distance from crest (max positive displacement) to crest; same as distance from trough (max negative displacement) to trough.

Period (T) – Time it takes consecutive crests (or troughs) to pass a given point, i.e., the time required for one full cycle of the wave to pass by. Period is the reciprocal of frequency: T = 1 / f.

Frequency (f ) – The number of cycles passing by in a given time. The SI unit for frequency is the Hertz (Hz), which is one cycle per second.

Wave speed (v) – How fast the wave is moving (the disturbance itself, not how fast the individual particles are moving, which constantly varies). Speed depends on the medium. We’ll prove that v = λ f.

Amplitude & Wavelength

The red transverse wave has the same wavelength as the longitudinal wave in the spring. (P to Q is one full cycle.) Note that where the spring is most compressed, the red wave is at a crest, and where the spring is most stretched (rarified), the red wave is at a trough. The amplitude in the red wave is easy to see. In the longitudinal wave, the amplitude refers to how far a particle on the spring moves to the left or right of its equilibrium point. Often a graph like the red wave is used to represent a longitudinal wave. For sound, the y-axis might be pressure deviation from normal air pressure, and the x-axis might be time or position.

Frequency & Period

Riddle me this…�Why is the frequency of a wave the reciprocal of its period?

Period = seconds per cycle.

Frequency = cycles per second.

They’re reciprocals no matter what unit we use for time. A sound wave that has a frequency of 1,000 Hz has a period of �1 / 1,000 of a second. This means that 1,000 high pressure fronts are moving through the air and hitting your eardrum each second.

Speed, Wavelength, & Frequency

Barney Rubble, a.k.a. “Barney the Wave Watcher,” is excited because he just made a discovery: v = λ f. With some high tech, prehistoric equipment, Barney measures the wavelength of the incoming waves to be 18 ft. He counts 10 crests hitting the shoreline every minute. So,

10 crests pass any given point in a time of one minute. But 10 crests corresponds to a distance of 180 ft, which means the wave is traveling at 180 ft / min. This result is the product of wavelength and frequency, yielding the result:

Harmonic Waves

Imagine a whole bunch of equal masses hanging from identical springs. If the masses are set to bobbing at staggered time intervals, a snapshot of the masses forms a transverse wave. Each mass undergoes simple harmonic motion, and the period of each is the same. If the release of the masses is timed so that the masses form a sinusoid at each point in time, the wave is called harmonic. Right now, m 4 is peaking. A little later m 4 will be lower and m 3 will be peaking. The masses (the particles of the medium) bob up and down but do not move horizontally, but the wave does move horizontally.

Making a Harmonic Wave

A generator attached to a rope moves up and down in simple harmonic motion. This generates a harmonic wave in the rope. Each little piece of rope moves vertically just like the masses on the last slide. Only the wave itself moves horizontally. The time it takes the wave to move from P to Q is the period of the wave, T. The distance from P to Q is the wavelength, λ. So, the wave speed is given by: v = λ / T = λ f (since frequency and period are reciprocals).

Since the generator moves vertically in SHM, the vertical position of the black doo-jobber is given by: y(t) = A cos ω t. The doo-jobber’s period is given by T = 2π / ω . This is also the period of the wave.

Making a Non-harmonic Wave

If the black doo-jobber does not move in SHM, the wave it generates will not be harmonic. As long as the generator has some sort of periodic motion, the wave generated will have a well defined period and wavelength. Here the generator pauses at the high and low points, causing the wave to flatten.

If the wave had moved at a constant speed and changed direction instantly, a saw-tooth wave would have been the result. Sound is not �a transverse wave, but a graph of pressure vs. time as a sound waves pass by would look like a very few simple sinusoid in the case of a pure tone. It would be a very complicated wave if the sound is a musical instrument of someone’s voice.

Wave Speed on a Rope

If a pulse is traveling along a rope to the right at a speed v, from its point of view it’s still and the rope is moving to the left at a speed v. As the red segment of rope of length s rounds the turn in the pulse, a centripetal force must act on it. The tension in the rope is F, and the downward components of the tension vectors add to make the centripetal force.

F C = m v 2 / r 2 F sin (θ / 2) = m v 2 / r 2 F (θ / 2) = m v 2 / r

(since the sine of an angle ≈ the angle itself in radians)

F θ = m v 2 / r F r θ / m = v 2 F s / m = v 2

(since s = r θ )

(continued)

Wave Speed on a Rope (cont.)

If the rope is uniform density, then the mass per unit length is a constant. We’ll call this constant µ. Thus, µ = m / s. From the last slide we have:

v 2 = F s / m = F / µ

This shows that waves travel faster in materials that are stiff �(high tension) and light weight. Unit check: [N / (kg / m)] ½ � = [N m / kg ] ½ = [(kg m / s 2 ) m / kg ] ½ = [m 2 / s 2 ] ½ = m / s.

Reflection of Waves

Whenever a wave encounters different medium, some of the wave may be reflected back, and some of the wave penetrate and be absorbed or transmitted through the new medium. Light waves reflects off of objects. If it didn’t, we would only be able to see objects that emitted their own light. We see the moon because it’s reflecting sunlight. Sound waves also reflect off of objects, creating echoes. Water waves, seismic waves, and waves traveling on a rope all can reflect.

Transmission & Reflection

Let’s look at 4 different scenarios of a waves traveling along a rope. The link below has an animation of each.

• Hard boundary (fixed end): Reflected wave is inverted.
• Soft boundary (free end): Reflected wave is upright.
• Light rope to heavy rope: Reflected wave is faster and wider than transmitted wave. Transmitted wave is upright, but reflected wave is inverted (since to the thin rope, the thick rope is like a hard boundary).
• Heavy rope to light rope: Transmitted wave is faster, wider, and has a greater amplitude than reflected wave. Both waves are upright. (The transmitted wave is upright this time since, to the thick rope, the thin rope is like a soft boundary).

Frequency of Transmitted Waves

The frequency of a transmitted wave is always unchanged. Say a wave with a frequency of 5 Hz is traveling along a rope that changes thickness at some point. Since 5 pulses hit this point every second, 5 pulses will be transmitted every second. Since the speed will vary depending on the thickness of the rope, the wavelength must vary too.

Here a wave travels from a thin rope to a thick one. Because µ is larger in the thick rope, the wave is slower there. This causes the waves to “bunch up,”which means a decrease in wavelength. (For clarity the reflected waves are not shown here.)

Amplitude & Energy

The energy carried by a wave is proportional to the square of its amplitude:

Consider our masses on a string again. The amount of potential energy stored in a spring is given by: U = ½ k x 2 , where k is the spring constant and x is the distance from equilibrium. For m 1 or m 4 , U = ½ k A 2 . The other masses have kinetic energy but less potential. Since energy is conserved, the total energy any mass has

is ½ k A 2 . This shows that energy varies as the square �of the amplitude. The constant of proportionality depends on the medium.

Amplitude of Reflected & Transmitted �Waves: Light to Heavy

Back to Animation

When a pulse on the light rope reaches the interface, the heavy rope offers a lot of resistance. The heavy rope is not affected much by the light rope, so the transmitted pulse has a smaller amplitude. The reflected pulse’s amplitude diminishes since some of the light rope’s energy it transmitted to the heavy rope.

incident pulse

inverted reflected pulse

transmitted pulse

Amplitude of Reflected & Transmitted �Waves: Heavy to Light

When a pulse on the heavy rope reaches the interface, the light rope offers little resistance. The light rope is greatly affected by the heavy rope, so the transmitted pulse has a greater amplitude. The upright reflected pulse’s amplitude diminishes since some of the heavy rope’s energy it transmitted to the light rope.

upright reflected pulse

We’ve seen that when a wave reaches an interface (a change from one medium to another), part of the wave can be transmitted, and part can be reflected back. A rope is a 1-dimensional medium; in a 2-dimensional medium a transmitted wave can change direction. This is refraction —the bending of a wave as it passes from one medium to another. The most well know type of refraction is that of light bending as it passes from air to glass or water, which we’ll study in detail in a unit on light.

As ocean waves approach the shore at an angle, the part of the wave closer to shore begins to slow down because the water is shallower. This causes refraction, and the waves bend so that it the wave fronts (crests) come in nearly parallel with the shore. See pic on next slide. Even though the medium (water) doesn’t change, one of its properties does—the speed of the wave.

Refraction of Ocean Waves

Wave fronts are shown in white heading toward the beach. The water gets shallow at the bottom first, which causes the waves to slow down and bend, and the wavelength to decrease. By the time the waves reach shore, they’re nearly parallel to the shoreline. The effect can even be seen on islands, where winds nearly wrap around it and come toward the island from all sides.

Superposition

Check out this animation to see what happens when two pulses approach each other from opposite ends on a rope.

Superposition Animation

Note the following:

• The waves pass through each other unaffected by their meeting.
• As they’re passing through each other the waves combine to create a changing waveform.
• The displacement of the rope at any point in this “combo wave” is the sum of the displacements of the displacements of the original waves. In other words, we add amplitudes. This is called superposition .

Constructive & Destructive Interference

Constructive Interference

Waves are “in phase.” By super-position, red + blue = green. If red and blue each have amplitude A, then green has amplitude 2A.

Destructive Interference

Waves are “out of phase.” By superposition, red and blue completely cancel each other out, if their amplitudes and frequencies are the same.

Interference Animation

Wave Interference

Like force vectors, waves can work together or opposition. Sometimes they can even do some of both at the same time. Superposition applies even when the waves are not identical.

Constructive interference occurs at a point when two waves �have displacements in the same direction . The amplitude of the combo wave is larger either individual wave.

Destructive interference occurs at a point when two waves have displacements in opposite directions. The amplitude of the combo wave is smaller than that of the wave biggest wave.

Superposition can involve both constructive and destructive interference at the same time (but at different points in the medium).

When waves bounce off a barrier, this is reflection . When waves bend due to a change in the medium, this is refraction . When waves change direction as they pass around a barrier or through a small opening, this is diffraction . Refraction involves a change in wave speed and wavelength; diffraction doesn’t.

Diffraction of water happens as waves bend around a boat in a harbor. This is different than the refraction of waves near shore because the depth of water does not decrease around the boat like it does near shore. Diffraction is most noticeable when the wavelength is large compared to the obstacle or opening. Thus, no noticeable diffraction may occur if the boat in the harbor is very big.

The sound waves from an owl’s hoot travel a greater distance in the forest than a song bird’s call, because a low pitch owl hoot has a longer wavelength than a high pitch songbird call, and the owl’s waves are able to diffract around trees. Pics on next slide

Diffraction Pics

When waves pass a barrier they curve around it slightly. When they pass through a small opening, they spread out almost as if they had come from a point source. These effects happen for any type of wave: water; sound; light; seismic waves, etc.

Diffraction & Bats

Bats use ultrasonic sound waves (a frequency too high for humans to hear) to hunt moths. The reason they use ultrasound is because at lower frequencies much of the sound waves would have a wavelength close to the size of a moth, which means much of the sound would diffract around it.

Bats hunt by echolocation—bouncing sound waves off of prey and listening for the echoes, so they need to emit sound with a wavelength smaller that the typical moth, which means a high frequency is required. High frequency sound waves reflect off the moths rather than diffracting around them. If bats hunted bigger prey, we might have emitted sounds that we could hear.

We’ll learn more about diffraction when we study light.

Standing Waves

When waves on a rope hits a fixed end, it reflects and is inverted. This reflected waves then combine with oncoming incident waves. At certain frequencies the resulting superposition yields a standing wave , in which some points on the rope called nodes never move at all, and other points called antinodes have an amplitude twice as big as the original wave.

A rope of given length can support standing waves of many different frequencies, called harmonics , which are named based on the number of antinodes.

1 st Harmonic � ( The Fundamental ) �

�4th Harmonic

2 nd Harmonic

3 rd Harmonic

Animations:

Standing Waves (cont.)

It is important to understand that a standing is the result of the a wave interfering constructively and destructively with its reflection. Only certain wavelengths will interfere with themselves and produce a standing wave. The wavelengths that work depend on the length of the rope, and we’ll learn how to calculate them in the sound unit. (Standing waves are very important in music.)

Wavelengths that don’t work result in irregular patterns. A standing wave could be simulated with a series of masses on springs, as long as their amplitudes varied sinusoidally.

Standing Wave with Incident & Reflected Waves Shown Separately � (scroll down)

Standing Wave with Superposition Shown � (scroll down)

Objects that oscillate or vibrate tend to do so at a particular frequency called the natural frequency . For example, a pendulum will swing back and forth at a certain frequency that only depends on its length, and a mass on a spring will bob up in down at a frequency that depends on the mass and the spring constant. It is possible physically to grab hold of the pendulum or mass and force it to swing or bob at any frequency, but if no one forces them, each will swing of bob at its

own natural frequency. If left alone, friction will rob the masses of their energy, and their amplitudes will decay. If a periodic force, like an occasional push, matches the period of one of the masses, this is called resonance , and the mass’s amplitude will grow.

Resonance Animation

Resonance (cont.)

Tarzan is swinging through �the jungle, but he can’t quite �make it across the river to the �next tree. So, he asks Jane �for a little help. She obliges by giving him a push every time he’s just about to swing away from her. In order to maximize his amplitude to get him across the river, her pushing frequency must match his natural frequency. This is resonance. When resonance occurs her applied force does the maximum amount of positive work. If she mis-times the push, she might do negative work, which would diminish his amplitude. The moral of the story is: Resonance involves timing and matching the natural frequency of an oscillator. When it happens, the oscillator’s amplitude increases.

Jane does �positive �work

Jane does �negative �work

Resonance Question

Explain how you could get a 700 lb wrecking ball swing with a large amplitude only by pulling on it with a scrawny piece of dental floss. answer :

Wrecking �Ball

Give the ball a little tug, as much as you can without breaking the floss. The ball with barely budge. Continue giving it tugs every time the ball is at its closest to you. If you match the natural frequency of the ball, its amplitude will slowly increase to the desired amount. In this way you are adding energy to the ball very slowly.

Tacoma Narrows Bridge

Even bridges have resonant (natural) frequencies. The Tacoma Narrows bridge in Washington state collapsed due to the complicated effects of wind. One day in 1940 the wind blew at just the right speed. The wind was like Jane pushing Tarzan, and the bridge was like Tarzan. The bridge twisted and shook

violently for about an hour. Eventually, the vibrations caused the by wind grew in amplitude until the bridge was destroyed.

Click the pic to see the �MPEG video clip.

The following images were obtained for these websites:

Marvin the Martian http://store.yahoo.com/rnrdist/warnerbrothers.html

Charlie Brown & Snoopy http://www.snoopy.com/

Godzilla http://www.cinescape.com/godzilla/

Drum & Bugle Corps (Cavaliers of Rosemont, IL) http://www.cavaliers.org/

Sand Scorpion http://www.aps.org/meet/MAR00/baps/vpr/layy3-03-04.html

Beach pic http://www.ssdsupply.com/hawaii.htm

Diffraction http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l3d.html � http://hea-www.harvard.edu/ECT/the_book/Chap1/Chapter1.html

Wave movies: Dr. Ken Russel, Kettering University http://www.kettering.edu/~drussell/Demos.html

Standing wave animated gifs: Tom Henderson, Glenbrook South High School http://www.physicsclassroom.com/Class/waves/U10L4b.html

Tacoma Narrows Bridge: http://www.civeng.carleton.ca/Exhibits/Tacoma_Narrows/DSmith/fig06.gif

13.1 Types of Waves

Section learning objectives.

By the end of this section, you will be able to do the following:

• Define mechanical waves and medium, and relate the two
• Distinguish a pulse wave from a periodic wave
• Distinguish a longitudinal wave from a transverse wave and give examples of such waves

Teacher Support

The learning objectives in this section will help your students master the following standards:

• (A) examine and describe oscillatory motion and wave propagation in various types of media.

Section Key Terms

Mechanical Waves

What do we mean when we say something is a wave? A wave is a disturbance that travels or propagates from the place where it was created. Waves transfer energy from one place to another, but they do not necessarily transfer any mass. Light, sound, and waves in the ocean are common examples of waves. Sound and water waves are mechanical waves ; meaning, they require a medium to travel through. The medium may be a solid, a liquid, or a gas, and the speed of the wave depends on the material properties of the medium through which it is traveling. However, light is not a mechanical wave; it can travel through a vacuum such as the empty parts of outer space.

A familiar wave that you can easily imagine is the water wave. For water waves, the disturbance is in the surface of the water, an example of which is the disturbance created by a rock thrown into a pond or by a swimmer splashing the water surface repeatedly. For sound waves, the disturbance is caused by a change in air pressure, an example of which is when the oscillating cone inside a speaker creates a disturbance. For earthquakes, there are several types of disturbances, which include the disturbance of Earth’s surface itself and the pressure disturbances under the surface. Even radio waves are most easily understood using an analogy with water waves. Because water waves are common and visible, visualizing water waves may help you in studying other types of waves, especially those that are not visible.

Water waves have characteristics common to all waves, such as amplitude , period , frequency , and energy , which we will discuss in the next section.

Misconception Alert

Many people think that water waves push water from one direction to another. In reality, however, the particles of water tend to stay in one location only, except for moving up and down due to the energy in the wave. The energy moves forward through the water, but the water particles stay in one place. If you feel yourself being pushed in an ocean, what you feel is the energy of the wave, not the rush of water. If you put a cork in water that has waves, you will see that the water mostly moves it up and down.

[BL] [OL] [AL] Ask students to give examples of mechanical and nonmechanical waves.

Pulse Waves and Periodic Waves

If you drop a pebble into the water, only a few waves may be generated before the disturbance dies down, whereas in a wave pool, the waves are continuous. A pulse wave is a sudden disturbance in which only one wave or a few waves are generated, such as in the example of the pebble. Thunder and explosions also create pulse waves. A periodic wave repeats the same oscillation for several cycles, such as in the case of the wave pool, and is associated with simple harmonic motion. Each particle in the medium experiences simple harmonic motion in periodic waves by moving back and forth periodically through the same positions.

[BL] Any kind of wave, whether mechanical or nonmechanical, or transverse or longitudinal, can be in the form of a pulse wave or a periodic wave.

Consider the simplified water wave in Figure 13.2 . This wave is an up-and-down disturbance of the water surface, characterized by a sine wave pattern. The uppermost position is called the crest and the lowest is the trough . It causes a seagull to move up and down in simple harmonic motion as the wave crests and troughs pass under the bird.

Longitudinal Waves and Transverse Waves

Mechanical waves are categorized by their type of motion and fall into any of two categories: transverse or longitudinal. Note that both transverse and longitudinal waves can be periodic. A transverse wave propagates so that the disturbance is perpendicular to the direction of propagation. An example of a transverse wave is shown in Figure 13.3 , where a woman moves a toy spring up and down, generating waves that propagate away from herself in the horizontal direction while disturbing the toy spring in the vertical direction.

In contrast, in a longitudinal wave , the disturbance is parallel to the direction of propagation. Figure 13.4 shows an example of a longitudinal wave, where the woman now creates a disturbance in the horizontal direction—which is the same direction as the wave propagation—by stretching and then compressing the toy spring.

Tips For Success

Longitudinal waves are sometimes called compression waves or compressional waves , and transverse waves are sometimes called shear waves .

Teacher Demonstration

Transverse and longitudinal waves may be demonstrated in the class using a spring or a toy spring, as shown in the figures.

Waves may be transverse, longitudinal, or a combination of the two . The waves on the strings of musical instruments are transverse (as shown in Figure 13.5 ), and so are electromagnetic waves, such as visible light. Sound waves in air and water are longitudinal. Their disturbances are periodic variations in pressure that are transmitted in fluids.

Sound in solids can be both longitudinal and transverse. Essentially, water waves are also a combination of transverse and longitudinal components, although the simplified water wave illustrated in Figure 13.2 does not show the longitudinal motion of the bird.

Earthquake waves under Earth’s surface have both longitudinal and transverse components as well. The longitudinal waves in an earthquake are called pressure or P-waves, and the transverse waves are called shear or S-waves. These components have important individual characteristics; for example, they propagate at different speeds. Earthquakes also have surface waves that are similar to surface waves on water.

Energy propagates differently in transverse and longitudinal waves. It is important to know the type of the wave in which energy is propagating to understand how it may affect the materials around it.

Watch Physics

Introduction to waves.

This video explains wave propagation in terms of momentum using an example of a wave moving along a rope. It also covers the differences between transverse and longitudinal waves, and between pulse and periodic waves.

• After a compression wave, some molecules move forward temporarily.
• After a compression wave, some molecules move backward temporarily.
• After a compression wave, some molecules move upward temporarily.
• After a compression wave, some molecules move downward temporarily.

Fun In Physics

The physics of surfing.

Many people enjoy surfing in the ocean. For some surfers, the bigger the wave, the better. In one area off the coast of central California, waves can reach heights of up to 50 feet in certain times of the year ( Figure 13.6 ).

How do waves reach such extreme heights? Other than unusual causes, such as when earthquakes produce tsunami waves, most huge waves are caused simply by interactions between the wind and the surface of the water. The wind pushes up against the surface of the water and transfers energy to the water in the process. The stronger the wind, the more energy transferred. As waves start to form, a larger surface area becomes in contact with the wind, and even more energy is transferred from the wind to the water, thus creating higher waves. Intense storms create the fastest winds, kicking up massive waves that travel out from the origin of the storm. Longer-lasting storms and those storms that affect a larger area of the ocean create the biggest waves since they transfer more energy. The cycle of the tides from the Moon’s gravitational pull also plays a small role in creating waves.

Actual ocean waves are more complicated than the idealized model of the simple transverse wave with a perfect sinusoidal shape. Ocean waves are examples of orbital progressive waves , where water particles at the surface follow a circular path from the crest to the trough of the passing wave, then cycle back again to their original position. This cycle repeats with each passing wave.

As waves reach shore, the water depth decreases and the energy of the wave is compressed into a smaller volume. This creates higher waves—an effect known as shoaling .

Since the water particles along the surface move from the crest to the trough, surfers hitch a ride on the cascading water, gliding along the surface. If ocean waves work exactly like the idealized transverse waves, surfing would be much less exciting as it would simply involve standing on a board that bobs up and down in place, just like the seagull in the previous figure.

Additional information and illustrations about the scientific principles behind surfing can be found in the “Using Science to Surf Better!” video.

• The surfer would move side-to-side/back-and-forth vertically with no horizontal motion.
• The surfer would forward and backward horizontally with no vertical motion.

Check Your Understanding

Use these questions to assess students’ achievement of the section’s Learning Objectives. If students are struggling with a specific objective, these questions will help identify such objective and direct them to the relevant content.

• A wave is a force that propagates from the place where it was created.
• A wave is a disturbance that propagates from the place where it was created.
• A wave is matter that provides volume to an object.
• A wave is matter that provides mass to an object.
• No, electromagnetic waves do not require any medium to propagate.
• No, mechanical waves do not require any medium to propagate.
• Yes, both mechanical and electromagnetic waves require a medium to propagate.
• Yes, all transverse waves require a medium to travel.
• A pulse wave is a sudden disturbance with only one wave generated.
• A pulse wave is a sudden disturbance with only one or a few waves generated.
• A pulse wave is a gradual disturbance with only one or a few waves generated.
• A pulse wave is a gradual disturbance with only one wave generated.

What are the categories of mechanical waves based on the type of motion?

• Both transverse and longitudinal waves
• Only longitudinal waves
• Only transverse waves
• Only surface waves

In which direction do the particles of the medium oscillate in a transverse wave?

• Perpendicular to the direction of propagation of the transverse wave
• Parallel to the direction of propagation of the transverse wave

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute Texas Education Agency (TEA). The original material is available at: https://www.texasgateway.org/book/tea-physics . Changes were made to the original material, including updates to art, structure, and other content updates.

Access for free at https://openstax.org/books/physics/pages/1-introduction

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• Publisher/website: OpenStax
• Book title: Physics
• Publication date: Mar 26, 2020
• Location: Houston, Texas
• Book URL: https://openstax.org/books/physics/pages/1-introduction
• Section URL: https://openstax.org/books/physics/pages/13-1-types-of-waves

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The Nature of Waves

A wave is a disturbance that propagates through a medium. There are three words in that definition that may need unpacking: disturbance, propagate, and medium.

• a change in a kinematic variable like position, velocity, or acceleration;
• a change in an intensive property like pressure, density, or temperature;
• a change in field strength like electric field strength, magnetic field strength, or gravitational field strength.
• To propagate , in the sense used in this definition, is to transmit the influence of something in a particular direction. Synonyms for propagate include spread, transmit, communicate, and broadcast. The noun form of the word is propagation .
• A medium is the substance through which a wave can propagate. Water is the medium of ocean waves. Air is the medium through which we hear sound waves. The electric and magnetic fields are the medium of light. People are the medium of a stadium wave. The Earth is the medium of seismic waves (earthquake waves). Cell membranes are the medium of nerve impulses. Transmission lines are the medium of alternating current electric power. Medium is the singuar form of the noun. Media is the plural form (although mediums is prefered by some people).

Let's list a few key examples of wave phenomena and then connect them to this definition. The first example that comes to mind when most people hear the word wave are the kinds of waves that one sees on the surface of a body of water: deep water waves in the ocean or ripples in a puddle. The most important kinds of waves for humans are the waves we use to sense the world around us: sound and light.

Imagine a calm pool. The surface is flat and smooth. Drop a rock into it. Kerploop. The surface is now disturbed. It is higher than normal in some places and lower than normal in others. The disturbed water at the point of impact disturbs the water next to it, which in turn disturbs the water next to it, which disturbs the water next to it, and so on. The disturbance spreads outward, transmits, or propagates. The medium through which this disturbance propagates is the surface of the water.

Imagine a quiet room. The air inside is still. Drop a book onto a table in that room. Thwap. The air between the book and the table is squeezed out in a fraction of a second. The air pressure in that rapidly decreasing gap rises above normal and then rebounds. The rise and fall of pressure is like the rise and fall of the surface of the pool in the previous example. The air under the book bumps the air on the edges of the book, which bumps the air next to it, which bumps the air next to it, and so on. The medium through which this disturbance propagates is the air.

Those were the easy examples. Water waves and sound waves are examples of mechanical waves — waves that propagate through a material medium. Light is not so easy to understand as a wave, which is why there are multiple sections of this book devoted to it. Still, I am going to try to describe it briefly.

Imagine a dark cavern, deep within the Earth. The electric and magnetic fields inside are relatively static and unchanging. Strike a match. Skeerach. The atoms of carbon in the wood of the matchstick combine with the atoms of oxygen in the air releasing heat. The heat agitates the atoms of the combustion products resulting in the phenomenon known as fire. The electrons bound to the rapidly vibrating atoms disturb the electric and magnetic fields in the space surrounding them. These fields are "elastic" in a sense. A wiggle in the fields in one place causes a wiggle in the fields nearby, which causes a wiggle in the fields nearby, and so on. These wiggles eventually make it to your eye, which you perceive as light. The electric and magnetic fields that fill all of space are the medium.

essential property

Waves transfer energy, momentum, and information, but not mass.

A naive description of a wave is that it has something to do with motion. But the motion of a wave on the water is not the same as the motion of the water from a hose. When waves move over the surface of the ocean, where does the ocean go? Nowhere. When waves reach the shore, does the water accumulate into great heaps? No. The water moves in and out, and the ocean stays behind. Even when huge tsunamis strike, the wall of water deposited on the land eventually drains back into the sea. In this case, no net transfer of mass has occurred.

Compare this to the water from a hose. The water comes pouring out the open end and stays where it lands forming a puddle or drains away to some other location. It most certainly does not jump back into the hose. In this case, mass has been transferred from one location to another.

Any sensible person who owns waterfront property should be familiar with the word erosion. Ocean waves (or waves on the Great Lakes for that matter) break on the shore, beating the rock and soil into submission and pulling it away. This material will never return. (If there were no plate tectonic forces lifting the land up in some places or volcanoes creating new land in others, the Earth would be covered in a global sea of uniform depth.) A force ( F ) has been exerted and mass has been displaced ( ∆ s ). Work has been done ( W  =  F ∆ s ). The ability to do work is one definition of energy ( W  = ∆ E ). Thus waves transfer energy.

Sticking with the example of ocean waves, anyone who surfs knows that waves transfer momentum. I have less to say on this subject.

Sound and light are the two primary examples of the way we gather information around us as humans. We have specialized sensory organs called ears and eyes for doing just that.

Here's a list of some phenomena or activities that satisfy the definition of a wave given above.

• including hock waves
• Radio waves
• Visible light
• Ultraviolet
• Tsunamis (tidal waves)
• Ripples (capillary waves)
• P waves (primary waves, pressure waves)
• S waves (secondary waves, shear waves)
• R waves (Rayleigh waves, ground roll)
• L waves (Love waves)
• A fluttering flag
• Snapping a sheet when making a bed
• Nerve impulses
• Peristalsis
• Heart contractions
• Snakes, eels, etc
• Worms, slugs, etc.
• Centipedes, millipedes, caterpillars, etc.
• Plucking, bowing, or striking a guitar, violin, or piano string
• Casting loops when fly fishing
• Cracking a whip
• Gravitational waves (as described in general relativity, not to be confused with gravity waves in water)
• Matter waves (quantum mechanical waves, de Broglie waves)
• Dominoes (as a show, not as a game)
• Stadium wave (Mexican wave, the wave)
• Newton's cradle (paid link)

not examples

Just because the word wave is used doesn't mean the thing being described is a wave in the sense used in this book.

• Waving as a signal to get someone's attention or to greet them or to say goodbye is not a wave. It does not propagate in a direction. Just because you wave at me does not mean that I have to start waving followed by a person behind me and the person behind them and the person behind them.
• A permanent wave set in a person's hair is not a wave. The term is almost an oxymoron. Nothing's moving if a thing is permanent. Also, you getting a wave set in your hair does not result in the people nearest you getting one followed by the people next to them getting one, and so on, until the whole globe is filled with wavy haired people.
• Wheat, or any other tall grass, is sometimes said to wave when gusts of wind pass over it. That bulk flow of matter is not a wave and neither is the response of the wheat.
• A heat wave is a meteorological term referring to a prolonged period of unusually high temperature. This definition has no connection to a phenomenon that propagates. Just because it's hot for a long period in one location does not imply that the heat wave will propagate to another location. It's actually sort of the opposite. A heat wave is often a region where the hot air is "stuck". The opposite of a heat wave could be called a cold wave, but it's usually described a cold snap (at least in the dialect of English I'm used to hearing). This should indicate that neither one of these phenomena is really a wave. Sometimes infrared radiation is described colloquially as heat waves, but that's not the right term. The same goes for rising thermals in the desert. That shimmering effect sometimes seen on the horizon is turbulent air of different density streaming upward and not a wave. Waves do not transfer mass.
• A crime wave is like a heat wave, but for crime. Since heat waves aren't waves, neither are crime waves.
• Making waves, meaning to stir up trouble, is not an example of a wave — and don't you disagree with me you trouble maker.

Classification of waves

Waves can be classified according to the medium through which they propagate.

by the type of disturbance

Waves can be classified according to the type of disturbance — meaning its relative direction or shap. There is a lot that can be said about this organizational scheme. I'm starting this part of this section with a quick summary in table form followed by a rather detailed follow up.

transverse waves

A transverse wave is one in which the direction of the disturbance is perpendicular to the direction of propagation. The word transverse describes something pointing in a sideways or lateral direction. As dynamic phenomena, waves are better represented with animations than with static images. Click on the static image below to see a transverse wave in action.

A cartoon representation of this kind of wave is your classic wiggly line. People with a bit of math knowledge will tell you they drew a sine curve. Those with a little bit more math knowledge will say they drew a sine or cosine curve.

The high parts on a curve like this are called crests . The low parts are called troughs . Since directions like up and down don't always make sense for waves, what the parts really represent are the maximal changes. The points labeled crests are points corresponding to a maximal increase of the changing quantity in a whatever direction is decided to be positive. The points labeled troughs are the points corresponding to the maximal change in the opposite direction.

Pronouncing words ending in -ough in English is often a mystery. The word trough rhymes with off. A trough is what one uses to provide food and water to livestock and other domesticated animals — typically a long, narrow open container that an animal would dip its head down into. The word crest rhymes with best. A crest is something at the top of something. Many birds, usually male birds, have crests. Hills and mountains are are sometimes said to have crests. The crest on a men's sports jacket or a school uniform gets its name from the heraldic crests that were originally worn on knight's helmets above the visor. Crests are up high. Troughs are down low.

The most important example of a transverse wave for humans is light. Most of what I am about to say in the following bullets will really be discussed elsewhere in this book.

• Showing that light is a just wave was not easy before the 20th century. Now that we have easy access to lasers in the 21st century, it's less of a problem. Light can be made to interfere with itself and produce a pattern of what are called interference fringes . A laser and two or more closely spaced openings are all that is needed. The iridescence seen when gasoline is spilled on water, in some insects like scarab beetles and butterflies, and in pearls and the shells of mollusks is caused by thin film interference . Observing this wave behavior of light requires no special technology.
• Showing that light is a transverse wave was was also not easy before the 20th century. Now that we have easy access to polarized sunglasses and polarized electronic displays in the 21st century, it's less of a problem. Light can be shown to exhibit polarization . Try looking at certain electronic displays with polarized sunglasses. If the orientation of the sunglasses is perpendicular to the orientation of the display, the display will look dark (or really screwed up). If the orientation is parallel, the display will look normal (or closer to normal than when they were perpendicular).

Lots of musical instruments make use of transverse waves to generate their characteristic sound.

• The source of the sound that comes out of violins, guitars, pianos and other chordophones is the side to side motion of a nylon or metal string (or in the olden days, dried animal intestines). The parts of the string vibrate side to side, but the wave travels along the length of the string. These two directions are perpendicular, which makes the waves transverse. The vibrations of the string are also transmitted into the wooded bodies or sound boards of these instruments. These flat wooden parts are driven to flex in and out, but the energy propagates across the surface. The two directions here are also perpendicular.
• The source of the sound that comes out of drum heads, kazoos or other membranophones is the in and out vibration of some flat, membrane-like structure. The waves produced by striking, stroking, or humming into these devices generates waves that crisscross the object. Once again, the disturbance is perpendicular to the propagation.
• Most percussion instruments that are not drums are classified as idiophones . Cymbals, triangles, and xylophones produce sound by the vibration of the entire object or a piece that is not a string, membrane, or column of air. The waves set up in many of these instruments are transverse, but because the class is so large and varied there is probably an exception out there somewhere.

Some animals propel themselves by sending transverse waves down the length of their bodies.

• Fish use a variety of means for getting around but long, thin, tubular fish like eels, lamprey, and dogfish are what comes to mind when I think about locomotion by transverse waves. A wave of side to side motion starts at the head and propagates backward along the spine. This propels the fish forward.
• Snakes also have several mechanisms for propelling themselves. The one that is considered most "normal" is called lateral undulation and has the classic look of a transverse wave in a one-dimensional medium. Much like the fish described above, a wave starts at the head as side to side motion and propagates backward down the length of the snake. A fancier kind of locomotion that relies on transverse waves is called sidewinding and the snakes that use it live in sandy deserts or slippery mud flats — anywhere getting a good grip on the ground is difficult. It's still an example of a transverse wave, but it propels the snake diagonally instead of forward relative to its body axis.

longitudinal waves

• pressure, compression, density
• aerophones - vibrating columns of air (horns, whistles, organ pipes )
• primary (P) pressure
• invertebrates (worms)
• traffic jams
• density waves in spiral galaxies generate the arms
• compressions (a.k.a. condensation): the pressed part, the greatest positive pressure change, a region where the medium is under compression
• rarefactions (a.k.a. dilations): the stretched part, the lowest negative pressure change, a region where the medium is under tension

complex waves

classed by orientation of change

• P rimary (surface, compression, P ressure)
• S econdary (transverse, S hear), can't propagate through liquids
• L ove, ( L ateral shear)
• R ayleigh, (elliptical, plate waves, ground R oll), something like ocean waves, but elliptical instead of circular

torsional waves

By duration.

classified by duration

by appearance

Waves can be classified according to what they appear to be doing.

Now look at these pretty, moving pictures.

FREE K-12 standards-aligned STEM

curriculum for educators everywhere!

Find more at TeachEngineering.org .

• TeachEngineering

Waves and Wave Properties

Lesson Waves and Wave Properties

Grade Level: 8 (8-10)

(two 50-minute periods; can be over two days)

Lesson Dependency: None

Subject Areas: Biology, Physical Science, Science and Technology

NGSS Performance Expectations:

• Print lesson and its associated curriculum

Curriculum in this Unit Units serve as guides to a particular content or subject area. Nested under units are lessons (in purple) and hands-on activities (in blue). Note that not all lessons and activities will exist under a unit, and instead may exist as "standalone" curriculum.

• The Three Color Mystery
• Light Properties
• Exploring the Electromagnetic Spectrum
• Developing & Presenting Design Solutions: Waves Go Public!

TE Newsletter

Engineering connection, learning objectives, worksheets and attachments, more curriculum like this, introduction/motivation, lesson closure, vocabulary/definitions, user comments & tips.

Engineers apply their knowledge of waves to design an array of useful products and tools, many of which are evident in our everyday lives. For example: microwave ovens, x-ray machines, eyeglasses, tsunami prediction, radios and speakers. Engineers must understand all the properties of waves and how waves can differ from one another in order to design safe and effective products. To predict how tsunamis will travel after a ocean earthquake, engineers must understand wave properties and how they travel. Engineers also use their understanding of wave properties when designing electronics—to separate different types of waves so that radios tune in to the right stations, or so your cell phone only picks up the calls that you want. Before designing a solution to a challenge, engineers conduct research and gather information as a crucial part of the engineering design process. Through this legacy cycle lesson, students begin to gather the knowledge necessary to come up with a solution to the engineering challenge outlined in lesson 1 of this unit.

After this lesson, students should be able to:

• Explain that waves transfer energy, not matter.
• Distinguish between mechanical and electromagnetic waves.
• Summarize the major properties and behavior of waves, including (but not limited to) wavelength, frequency, amplitude, speed, refraction, reflection and diffraction.

Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .

Ngss: next generation science standards - science.

Common Core State Standards - Math

View aligned curriculum

Do you agree with this alignment? Thanks for your feedback!

International Technology and Engineering Educators Association - Technology

State standards, south carolina - science.

(In advance, make copies of the All About Waves—Notes Outline and Anatomy of a Wave Worksheet , one each per student, and have graph paper available for students. Also [optional], prepare to show students the attached 16-slide Waves and Wave Properties Presentation to accompany the lesson introduction. The slides are "animated" so you can click to show the next item when ready.)

Returning to our three-color mystery, today we are going to develop an understanding of the fundamental concepts of waves. What we learn will move us one step closer to reaching our goal of creating a solution to our engineering challenge that I explained yesterday (lesson 1 of this unit).

Let's start with what we already know. Why are we able to see? (Because there is light.) What is light? (It is a wave.) So, what is a wave? Well, we will learn the answer to that question today!

I will pass out an outline that will help you keep track of the important concepts explained as we talk about waves and wave properties.

(At this point, hand out the notes outlines and present the lecture material provided in the Background section, in tandem with the slides.)

(Next, so students can apply what they just learned, divide the class into groups of two students each, and hand out copies of the worksheets and blank graph paper.)

Who has ever sunburned your skin? Who has used a microwave to make popcorn? Or had an x-ray taken? Or listened to the radio? What do these activities have in common? (Listen to student answers.) All of these require waves.

One difference between the waves that pop popcorn and the waves that tan your skin is wave frequency. As we have learned, the frequency of a wave is defined as the number of cycles that pass a single point in a given amount of time.

In the first part of the worksheet, label the parts of a wave using the definitions given. Then, draw four different waves given information about the waves' properties. Of these four waves, your challenge is to identify the ones with the highest and lowest frequencies.

Lesson Background and Concepts for Teachers

(The following lecture material aligns with the slides.)

A wave is a disturbance that carries energy from one place to another. Matter is NOT carried with the wave! A wave can move through matter (called a "medium"), but some waves do not need a medium to be able to move. If a wave needs a medium, we call it a mechanical wave. If a wave can travel without a medium, (for example, through space), we call it an electromagnetic wave.

• Transverse waves : Waves in which the medium moves at right angles to the direction of the wave. Think about a "stadium wave:" the people are moving up and down, but the wave is going around the stadium. Parts of transverse waves:
• Crest: the highest point of the wave
• Trough: the lowest point of the wave
• Compressional (longitudinal) waves : Waves in which the medium moves back and forth in the same direction as the wave. Parts of compressional waves:
• Compression: where the particles are close together
• Rarefaction: where the particles are spread apart

Wave properties depend on what (type of energy) makes the wave. For example, you splashing in the ocean or an earthquakes creating a tsunami. Descriptive wave properties include:

• Wavelength : The distance between one point on a wave and the exact same place on the next wave.
• Frequency: How many waves go past a point in one second. The unit of measurement is hertz (Hz). The higher the frequency, the more energy in the wave.
• If 10 waves go past in 1 second, it is 10 Hz
• If 1,000 waves go past in 1 second, it is 1,000Hz
• If 1,000,000 waves go past, it is 1,000,000 Hz
• Amplitude : How far the medium (crests and troughs, or compressions and rarefactions) moves from rest position (the place the medium is when not moving). The more energy a wave carries, the larger its amplitude.
• The energy of a wave can be expressed by the equation E = CA 2 , where E is energy, C is a constant dependent upon the medium, and A is the amplitude.
• Wave speed : Depends on the medium in which the wave is traveling. It varies in solids, liquids and gases. A mathematical way to calculate wave speed is: wave speed = wavelength (in m) x frequency (in Hz). Or, v = f x λ. So, if a wave has a wavelength of 2 m and a frequency of 500 Hz, what is its speed? (Answer: wave speed = 2 m x 500Hz = 1000 m/s)

Changing Wave Direction

• Reflection : When waves bounce off a surface. If the surface is flat, the angle at which the wave hits the surface will be the same as the angle that the wave leaves the surface. In other words, the angle in equals the angle out. This is the law of reflection . (For example, when a pool ball strikes the side of a pool table, the angle at which it hits the bumper is the same angle at which it bounces off the bumper.)
• Refraction : Waves can bend. This happens when a wave enters a new medium and its speed changes. The amount of bending depends on the medium it is entering . (optional: To explain this phenomenon in more detail, search the Internet to find an interactive tutorial that shows light being bent as it travels through a medium.)
• Diffraction : The bending of waves around an object. The amount of bending depends on the size of the obstacle and the size of the waves. (optional: To explain this phenomenon in more detail, search the Internet to find an interactive tutorial that shows the diffraction of monochromatic light through slits of varying widths.)
• Large obstacle, small wavelength = low diffraction (bending)
• Small obstacle, large wavelength = large diffraction (bending)

Now that you're all experts in understanding the different types of waves, how they move and change direction, and how to describe their characteristics, tell me, what are some of the ways that you see waves used in your everyday lives? (Listen to student ideas.) Those are great examples. What about microwave ovens, medical and dental x-ray machines, eyeglasses and speakers? These are common examples in which engineers apply their knowledge of waves to design all types of useful products and tools that are evident in our everyday lives. To design these products, engineers must be well versed in all the properties of waves and how waves can differ from one another. For example, the waves emitted from a microwave are very different than those emitted from an x-ray machine that creates images of bones or teeth. Engineers need a complete understanding of wave properties in order to design safe and effective products!

But that's not all—engineers work to protect people and predict how tsunamis will travel after an earthquake in the ocean by using wave properties. To successfully predict where a tsunami will travel, engineers must understand how waves move and the properties associated with waves.

Another example of engineers using wave properties is when electrical engineers separate different types of waves so that the radio you are using tunes in to the right station, or your cell phone only picks up the calls that you want. If it were not for these engineers, you would constantly be getting calls from people you did not know. To accomplish this they must have a clear understanding of wave properties and know how to separate different types of waves.

Before designing and creating a solution to a challenge, engineers conduct research and gather information, just like you did today. This step is a crucial part of the engineering design process.

amplitude: How far the medium (crests and troughs, or compressions and rarefactions) moves from rest position (the place the medium is when not moving).

compression: When the particles of a longitudinal wave are close together.

compressional (longitudinal) wave: A wave in which the medium moves back and forth in the same direction as the wave.

crest: The highest point on a transverse wave.

diffraction: The bending of waves around an object.

electromagnetic wave: A wave that does not require a medium to travel, for example, it can travel through a vacuum. Also called an EM wave.

energy: The capacity to do work.

frequency: How many waves go past a point in one second. Measured in hertz (Hz).

mechanical wave: A wave that requires a medium to travel.

rarefaction : When the particles of a longitudinal wave are far apart.

reflection: When a wave bounces off a surface.

refraction: When a wave bends.

transverse wave: A wave in which the medium moves at right angles to the direction of the wave.

trough: The lowest point on a transverse wave.

wave: A disturbance that carries energy from one place to another.

wavelength: Distance between one point on a wave and the exact same place on the next wave.

Note Taking : During the lecture, have students complete the All About Waves—Notes Outline and refer to it for visuals that supplement the lecture material. Then, with the notes turned over on their desks, ask students various questions that were covered in the lecture material. Evaluate students' answers to gauge their mastery of the subject.

Worksheet : After the lecture, have students complete the Anatomy of a Wave Worksheet to see how well they apply what they learned.

Trade-n-Test : To conclude, have each student make up their own wave properties (that is, trough and crest height and wavelength) and write it down. Then have students trade the "invented properties" papers with other students and draw the new waves based on the given properties.

Students learn the basic properties of light — the concepts of light absorption, transmission, reflection and refraction, as well as the behavior of light during interference. Lecture information briefly addresses the electromagnetic spectrum and then provides more in-depth information on visible li...

Students learn about the science and math that explain light behavior, which engineers have exploited to create sunglasses. They examine tinted and polarized lenses, learn about light polarization, transmission, reflection, intensity, attenuation, and how different mediums reduce the intensities of ...

Students learn about the basic properties of light and how light interacts with objects. They are introduced to the additive and subtractive color systems, and the phenomena of refraction. Students further explore the differences between the additive and subtractive color systems via predictions, ob...

Students learn about glaucoma—its causes, how it affects individuals and how biomedical engineers can identify factors that trigger or cause this eye disease, specifically the increase of pressure in the eye. Students sketch their own designs for a pressure-measuring eye device, prepare them to cond...

Davidson, Michael W. Diffraction of Light, Physics of Light and Color, Optical Microscopy Primer. Last modified June 15, 2006. Florida State University and the National High Magnetic Field Laboratory, Optical Microscopy, Molecular Expressions. Accessed February 7, 2012. http://micro.magnet.fsu.edu/primer/java/diffraction/basicdiffraction/index.html

Davidson, Michael W. Particle and Wave Refraction, Physics of Light and Color, Optical Microscopy Primer. Last modified June 15, 2006. Florida State University and the National High Magnetic Field Laboratory, Optical Microscopy, Molecular Expressions. Accessed February 7, 2012. http://micro.magnet.fsu.edu/primer/java/particleorwave/refraction/index.html

Lewis, Susan K. Anatomy of a Tsunami. Posted March 29, 2005. Nova beta, PBS Online by WGBH. Accessed February 7, 2012. http://www.pbs.org/wgbh/nova/tsunami/anatomy.html

Sound & Light: Chapter 1, Section 2 Properties of Waves. Quia, IXL Learning. Accessed February 7, 2012. http://www.quia.com/rr/221617.html

Other Related Information

Browse the NGSS Engineering-aligned Physics Curriculum hub for additional Physics and Physical Science curriculum featuring Engineering.

Contributors

Supporting program, acknowledgements.

This lesson was developed through Clemson University's "Engineering Fibers and Films Experience – EFF-X" Research Experience for Teachers program, funded by National Science Foundation grant no. EEC-0602040. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: December 4, 2023

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Types of Waves.

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Types of Waves

Apr 03, 2019

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Random Waves. Types of Waves. Properties of Waves. Wave Measurement. Matter & Waves. 200. 200. 200. 200. 200. 400. 400. 400. 400. 400. 600. 600. 600. 600. 600. 800. 800. 800. 800. 800. 1000. 1000. 1000. 1000. 1000.

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• resting point
• speed wavelength
• waves wave measurement matter
• wave measures

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Random Waves Types of Waves Properties of Waves Wave Measurement Matter & Waves 200 200 200 200 200 400 400 400 400 400 600 600 600 600 600 800 800 800 800 800 1000 1000 1000 1000 1000

Which type of mechanical wave looks like a rollercoaster and was demonstrated in the slinky lab? 200

Transverse Wave 200

Which type of wave does NOT need a medium to travel through? 400

An Electromagnetic Wave 400

Which type of wave measures its wavelength from crest to crest, trough to trough or normal to normal? 600

Transverse Wave 600

Sound is an example of THIS type of wave…. 800

Longitudinal Wave 800

Give an example of an electromagnetic wave and explain why. 1000

Light because light doesn’t need a medium to travel through such as all electromagnetic waves. 1000

The area of a longitudinal wave that is spread apart is known as its: 200

Rarefaction 200

The resting point of the transverse wave is known as its… 400

How often energy passes through is known as its… 600

Frequency 600

What is NOT carried along with the energy of the wave, but continues to move. 800

The particles of the wave 800

A wave that occurs at the boundary between two mediums is known as… 1000

A surface wave 1000

The speed of a wave is determined by measuring _________ x _______. 200

Frequency , wavelength 200

The measurement of a wave’s energy is called its: 400

Amplitude 400

The wavelength of a longitudinal wave can be measured two ways. Name them. 600

Compression to compression.Rarefaction to rarefaction 600

If the frequency of a wave increases, its wavelength _______.If the frequency of a wave decreases, its wavelength ________. 800

Decreases, Increases 800

A wave has a wavelength of 6 m, and a speed of 480 mph. What is the frequency at which the wave travels? 1000

80 Hertz 1000

The molecule arrangement in the box represents which type of matter? 200

Which state of matter is the most dense? 400

A solid 400

Which state of matter has an indefinite shape and an indefinite volume? 600

Explain why the gas, Helium helps sounds waves move more quickly through its particles compared to Oxygen. 800

Because Helium is lighter and therefore less dense, making it easier to travel through. Thus, the speed is faster. 800

Explain the movement of a wave in relation to its source. 1000

Outward, in all directions away from its source. 1000

Name one way in which amplitude is measured in a transverse wave. 200

From normal to crest or normal to trough 200

How is frequency measured? 400

Frequency = Speed/Wavelength 400

What is the length of time it takes for one full wave to pass a given point? 600

A period 600

Measuring how compressed or rarefied the longitudinal wave is, measures its….. 800

Amplitude 800

What to the particles in a transverse way do versus the particles in a longitudinal wave? 1000

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