longitudinal and transverse waves

Define transverse waves

Waves that oscillate at right angles to the direction of the energy propagation. (e.g. EM waves)

Define longitudinal waves.

Waves that oscillate parallel to the direction of the energy propagation. (e.g. sound waves)

Define compression and rarefaction

Compression- particles bunch up

Rarefaction- particles spread out

Define polarised waves.

A transverse wave that oscillates its particles or field (a physical quantity assigned to every point in space and time)through a single plane

A propagating ( travelling) disturbance that transfers energy and information from one location to another without transferring matter

How is polarisation evidence of transverse waves?

Because polarisation restricts oscillations to one plane, this mean waves have to be perpendicular to the waves direction of travel (because transverse waves have infinite possible orientations (choices) that can be filtered down to one specific plane.

Also there are an infinite number of planes perpendicular to the direction the wave is travelling. Think of it like a spiral but 2d

What is the difference between unpolarised and polarised?

Unpolarised waves oscillate in many planes (infinite 2d random direction) at right angles to the energy of propagation

Polarised waves oscillate in one plane

What does plane polarisation mean?

The path of vibration is oscillating in a 2d direction

Why can’t longitudinal waves be polarised?

Because they have lack the freedom to vibrate in different orientations (angles) -only one dimension of motion

Immunisation to filters: rotating a polarising filter around a longitudinal wave, the wave will remain unchanged- oscillations are parallel to the path of travel so lack the perpendicular motion for the filter to block (move back and forward along 1d)