This lesson will focus on what happens when a wave changes media or interacts with an obstacle or another wave. The first interaction we will look at is what happens when a wave hits a barrier. In the following demonstration, we look at a wave pulse reflecting back when it hits the end of a string.

Set the wave generator to pulse, and use the slider to set the damping to zero. Click "pulse."

What happens to the wave pulse when it hits the clamp at the end of the string?

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Check Your Answer

The pulse turns upside-down when it bounces back.

Click on the "reset" button.
Select "Loose End."
Click "pulse."

What happens to the pulse when it hits the end of the string?

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Check Your Answer

It remains upright when it bounces back.

This animation showed what happens in one dimension, but sometimes waves reflect in two or three dimensions. Think about it, what if a water wave or sound or light hits a solid object at an angle?

Watch this animation to find out.

Source: Optics, the Physics Classroom

How does the wave move when it reflects from the surface of the obstacle?

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Check Your Answer

The wave follows the law of reflection. θ_i = θ_r or the angle of incidence (that's the incoming wave) equals the angle of reflection.