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. Consider the simplified water wave in Figure 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. 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 In contrast, in a longitudinal wave , the disturbance is parallel to the direction of propagation.
Figure Longitudinal waves are sometimes called compression waves or compressional waves , and transverse waves are sometimes called shear waves. 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 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 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 wave is the disturbance people jumping up and sitting back down , and it travels around the stadium. However, none of the individual people in the stadium are carried around with the wave as it travels - they all remain at their seats. Check out this real-life example by a military precision drill team form Physics Footnotes.
Sound waves in air behave in much the same way. As the wave pulse passes through, the particles in the air oscillate back and forth about their equilibrium positions but it is the disturbance which travels, not the individual particles in the medium. There are several other examples of wave types which can propagate through a mechanical medium. Transverse waves on a string are another example.
Answer: D A wave is a continuous and repeating disturbance of a medium and a pulse is a single disturbance. What is a Wave? Answer: A In longitudinal waves, particles of the medium vibrate to and from in a direction parallel to the direction of energy transport. If energy is transmitted along a medium from the east end to the west end, then particles of the medium would vibrate eastward and westward A sound wave is a longitudinal wave but not the answer since a wave which exhibits this characteristic is not necessarily a sound wave.
Categories of Waves. Answer: D In transverse waves, particles of the medium vibrate to and from in a direction perpendicular to the direction of energy transport. Answer: A In transverse waves, particles of the medium vibrate to and from in a direction perpendicular to the direction of energy transport.
Answer: B In longitudinal waves, particles of the medium vibrate to and from in a direction parallel to the direction of energy transport. Categories of Wave. Answer: C The speed of a wave or a pulse depends upon the properties of the medium.
The Speed of a Wave. Answer: D The speed of a wave is dependent upon the properties of the medium and not the properties of the wave. Answer: B As a wave crosses a boundary into a new medium, its speed and wavelength change while its frequency remains the same. The Wave Equation. Answer: A The amplitude of a wave is measured from rest to crest or from rest to trough; but not from crest to trough. The Anatomy of a Wave.
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