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Waves

Reflection at a Point where the Wave Velocity Changes

When there is a change of medium, the wave velocity changes. When this happens, some of the energy of the incident wave is reflected and some is transmitted. In the examples below, imagine that the blue spring has a greater mass per unit length than the red spring, so the wave velocity is lower in the blue spring.

Transmitted wave, no phase change.
Reflected wave, phase change.
 

Transmitted wave, no phase change.
Reflected wave, no phase change.

 

© David Hoult 2008