They differ in how particles of the medium move when the energy of the wave passes through. At the following URL, read the short introduction to waves and watch the animations. Then answer the questions below. The article gives a dictionary definition of wave. What is the most important part of this definition? What happens to particles of the medium when a wave passes? What is the medium of a mechanical wave? List three types of mechanical waves. If you shake one end of a rope up and down, a wave passes through the rope.
Which type of wave is it? Can you guess what this picture shows? The objects are guitar strings, and the moving string is the one on the bottom right.
The string is moving because it has just been plucked. Plucking the string gave it energy , which is moving through the string in a mechanical wave. A mechanical wave is a wave that travels through matter. The matter a mechanical wave travels through is called the medium.
The type of mechanical wave passing through the vibrating guitar string is a transverse wave. A transverse wave is a wave in which particles of the medium vibrate at right angles, or perpendicular, to the direction that the wave travels.
Another example of a transverse wave is the wave that passes through a rope with you shake one end of the rope up and down, as in the Figure below. The direction of the wave is down the length of the rope away from the hand. The rope itself moves up and down as the wave passes through it. Q: When a guitar string is plucked, in what direction does the wave travel?
In what directions does the string vibrate? A: The wave travels down the string to the end. The string vibrates up and down at right angles to the direction of the wave. A transverse wave is characterized by the high and low points reached by particles of the medium as the wave passes through. The high points are called crests, and the low points are called troughs. You can see both in the Figure below. Transverse waves called S waves occur during earthquakes.
The disturbance that causes an earthquake sends transverse waves through underground rocks in all directions away from the disturbance.
S waves may travel for hundreds of miles. An S wave is modeled in the Figure below. At the following URL, review transverse waves and watch the animations. This must be a longitudinal wave. The fans will need to sway side to side. Thus, as the wave travels around the stadium they would be moving parallel to its direction of motion. If they rise up and sit down, then they would be creating a transverse wave. Mechanical waves require a medium in order to transport energy. Sound, like any mechanical wave, cannot travel through a vacuum.
A science fiction film depicts inhabitants of one spaceship in outer space hearing the sound of a nearby spaceship as it zooms past at high speeds. Critique the physics of this film. This is an example of faulty physics in film. Sound is a mechanical wave and could never be transmitted through the vacuum of outer space. If you strike a horizontal rod vertically from above, what can be said about the waves created in the rod? The particles vibrate in the direction of the source which creates the initial disturbance.
Since the hammer was moving vertically, the particles will also vibrate vertically. They travel in a direction that is at right angles to the direction of the particles of the medium. The characteristic described in statement c is a property of all transverse waves, but not necessarily of all mechanical waves. A mechanical wave can also be longitudinal. The sonar device on a fishing boat uses underwater sound to locate fish.
Would you expect sonar to be a longitudinal or a transverse wave? Only longitudinal waves are capable of traveling through fluids such as water. When a transverse wave tries to propagate through water, the particles of the medium slip past each other and so prevent the movement of the wave. Physics Tutorial. My Cart Subscription Selection. Student Extras.
Waves and Wavelike Motion What is a Wave? Categories of Waves. We Would Like to Suggest Why just read about it and when you could be interacting with it? Interact - that's exactly what you do when you use one of The Physics Classroom's Interactives. 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. 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. 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 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. 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.
If students are struggling with a specific objective, these questions will help identify such objective and direct them to the relevant content. What are the categories of mechanical waves based on the type of motion? In the figure above, the electric field in red is vertically polarized. Think of a throwing a Frisbee at a picket fence.
In one orientation it will pass through, in another it will be rejected. This is similar to how sunglasses are able to eliminate glare by absorbing the polarized portion of the light. The terms light, electromagnetic waves, and radiation all refer to the same physical phenomenon: electromagnetic energy. This energy can be described by frequency, wavelength, or energy.
All three are related mathematically such that if you know one, you can calculate the other two. Radio and microwaves are usually described in terms of frequency Hertz , infrared and visible light in terms of wavelength meters , and x-rays and gamma rays in terms of energy electron volts. This is a scientific convention that allows the convenient use of units that have numbers that are neither too large nor too small. The number of crests that pass a given point within one second is described as the frequency of the wave.
One wave—or cycle—per second is called a Hertz Hz , after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz.
Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet! An electromagnetic wave can also be described in terms of its energy—in units of measure called electron volts eV. An electron volt is the amount of kinetic energy needed to move an electron through one volt potential.
Moving along the spectrum from long to short wavelengths, energy increases as the wavelength shortens. Consider a jump rope with its ends being pulled up and down. More energy is needed to make the rope have more waves.
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