# Waves

A wave is a propagating disturbance that travels through matter (mechanical wave) or space (electromagnetic wave) transferring only energy.

## Properties

• A wave’s crest is its highest point, and its trough is its lowest point.
• A wave’s amplitude is the maximum distance (positive or negative) a wave reaches from its rest position.
• Wavelength is the distance between identical points on adjacent waves.
• Frequency is the amount of wave cycles per second.

A wave’s energy is proportional to its frequency. If a wave’s frequency doubles, its energy also doubles.

A wave’s energy is proportional to the square of its amplitude. If a wave’s amplitude doubles, its energy quadruples ($2^2 = 4$).

## Interaction

Transmission is when a wave passes from a medium into another. Refraction is the change in direction of a wave passing from one medium to another with a different density.

Absorption is when a wave loses energy as it transmits into a material. Reflection is the change in direction of a wave at a boundary or fixed end.