Interference

Where two waves meet, their effects are added together. This is called interference.

Constructive interference

When they arrive in step, they reinforce each other to give a wave of greater amplitude [amplitude: The maximum height of a wave, measured from the mid-point of its vibration. ].

This is called constructive interference.

Constructive interference

Destructive interference

When they arrive out of step, they cancel out.

This is called destructive interference.

Destructive interference

Interference of light

If a laser is shone on two slits very close together, the diffracted beam can be seen on a screen to have bright and dark bands on it.

Interference of light

The bright bands show constructive interference of light.

The dark bands show destructive interference of light.

Interference and diffraction of light and sound show that light and sound are both types of wave.

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