Table Of Contents: Wave Interactions
Imagine jumping into a pool. The wave hits the side of the pool and bounces back. This is called reflection. When the front of the wave meets a barrier it cannot go through or over, it will be reflected. When a sound wave is reflected we hear an echo. Light waves reflect off surfaces like a mirror or snow.
When a wave enters a new medium, the speed of the wave changes. If the wave enters the new medium at an angle part of the wave slows down. This makes the wave bend. This bending is called refraction. When water waves reach the beach, the shallower water acts like a new medium and will slow down the waves. Waves coming in at an angle to the shore will be bent. Light waves refract when the light passes from air to water as seen by the bent appearance of a straw in a glass of water.
Most of the time, waves travel in straight lines. However, when a wave reaches corners or openings in a barrier the wave bends and spreads out to fill the medium. This bending of waves is called diffraction. Water waves diffract as they pass around a barrier such as a pier. Sound waves diffract through openings or around corners.
Interference occurs when two or more waves meet in a medium and combine to form a single wave. Interference can be constructive or destructive. In constructive interference when the waves meet, their amplitudes add together to make a bigger wave. In destructive interference the amplitude of the waves subtract and can even cancel each other out completely. For both types of interference, once the waves meet they pass through each other unchanged.
5. Standing Waves
A special type of interference produces a standing wave. These waves are formed by the wave and its reflected wave. The two waves combine to form one wave that appears to be standing still. The wave must have a special frequency in order to produce this standing wave. Musical instruments use standing waves to produce music. Standing waves can also be destructive. If standing waves are produced in a structure, such as a bridge, the structure can collapse.