Chapter 15 Section 3

In reflection, waves meet a solid barrier and bounce back. For example, an echo occurs when a sound wave meets a wall and bounces back to the source of the sound.

In refraction, waves move from one medium to another and bend, or refract. An example is a glass of water with a straw. Where the straw passes into the water, it looks broken. But the break is an illusion caused by refraction of light waves as they pass from air to water.

In diffraction, waves interact with a partial barrier and a portion of the waves pass through and spread out. An example is the way sound waves spread around corners.

In constructive interference, two waves combine in phase, so that a crest meets a crest or a trough meets a trough.

In destructive interference, two waves of the same frequency meet up such that the trough of one wave joins with the crests of the other. If the amplitudes of the two original waves are equal, the two waves cancel each other out.