For all waves:
* The maximum displacement from equilibrium is reduced by half. This means the wave crests are half as high and the troughs are half as low.
* The intensity of the wave is reduced by a factor of four. Intensity is proportional to the square of the amplitude, so halving the amplitude reduces the intensity to one-fourth of its original value.
Specifically for sound waves:
* The loudness of the sound is decreased. The perceived loudness of sound is related to its intensity, so halving the amplitude would result in a quieter sound.
Specifically for light waves:
* The brightness of the light is reduced. The brightness of light is also related to its intensity, so halving the amplitude would result in dimmer light.
In summary: Halving the amplitude of a wave reduces its maximum displacement, intensity, and perceived loudness or brightness.
