Polarisation part 1
Polarisation is a process that occurs only with tranverse waves such as electromagnetic wabves
Tranverse waves can vibrate in many planes that are at 90 degress to the direction of wave propagation.
for example , a light bulb produces waves in all different possible planes at 90 degress to the sources. this is unpolarised ligtht.
POLARISATION PART 2
In plane polarized light , all waves are in the same plane as each other. This can be achieved by shining un-polarized light through a polarizing filter. the plane of the polarized light is a parallel filter.
if a second filter is added at a right angle to the first , no light gets through. this is because the planes of the polarized light is also at right angles to the second filter.
the intensity of light after it passes through a second filter is proportional to the relative angle of the two filters. As the angle increases to 90 degrees the intensity decreases. this is malus law.