Polarisation

Transverse waves can be plane-polarised.Waves are plane-polarised if all the oscillations are in one plane only.Transverse waves can be polarised because the direction of oscillations is not in the same direction as the direction of wave travel but is perpendicular.Longitudinal waves cannot be polarised because the direction of the oscillations is parallel to the direction the wave travels.A polaroid filter only allows light that is vibrating in a certain plane through.Polaroid sunglasses are used for fishing as they reduce the glare of light from the surface of water.Light reflected off the surface of water is polarised so its intensity is reduced when it passes through sunglasses. In this way the fisherman sees the contents of the pool and not the glare of light from the surface which would obscure his view of what is under the surface.