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# Chapter 12: Waves and Energy Transfer

Difficulty Level: At Grade Created by: CK-12

Of all sports, surfing uses waves and their properties most directly - a surfer's kinetic energy comes directly from the waves themselves. Of all the wave forms we will study, it is with water waves that we have the most personal experience. Water waves in large bodies of water, however, have movement that is NOT due to the natural characteristics of waves. In pure transverse waves (like water waves), the particles of media move perpendicularly to the direction of the energy movement. If we created a perfect water wave in a lab, the water molecules would move up and down only and the energy of the wave would move horizontally toward the sides of the pan. In such a perfect wave, the apparent movement of water toward the side of the pan is an illusion. After completing this chapter, you will understand different types of waves, as well as their properties.

Chapter Outline

### Chapter Summary

The primary topic of this chapter was wave motion. Mechanical waves are either transverse, like a swinging jumprope, or longitudinal, like a compressed slinky. Both types of waves have a wavelength, frequency, period, and wave velocity, which can be easily calculated. Waves are also subject to the Doppler effect, in which the apparent frequency of the waves is lesser or greater than the emitted frequency, depending on the relative speed of the two objects and whether they are approaching or retreating from each other. This effect explains why the pitch of an emergency siren changes as it approaches a listener. Finally, this chapter explained why and how waves are refracted and reflected as they move from one medium to another.