3 Mechanical Waves
Transverse waves require a medium to travel through like air or water. The crest is the top of the wave while the trough is a relative minimum. The Equilibrium is the line in the middle of the wave and the amplitude is the distance from the equilibrium to the top or bottom. The wavelength is the distance for one cycle which is from relative max to max.
Surface waves also require a medium to travel through. The Energy travels in circles as the motion of the wave continues in a circle. An example of such a wave is an ocean wave. The wave itself is traveling on the surface of a medium like an ocean. In this picture air and water are the two mediums in contact that make the surface waves.
Longitudinal waves also need a medium to travel through like air. An example of a longitudinal wave is a sound wave and the displacement of the medium is parallel to the propagation of the wave. The rarefaction of the wave is the part that is at a lower frequency while the compression of the wave is the part that is compressed and at a higher frequency. The energy of the wave goes in the direction of the wave. The wavelength is the distance from compression to compression.