What is polarized light?

When something emits light, the waves produced usually have their oscillation moving at all different angles. You can have some oscillating left and right, up and down, at a 45-degree angle, or any angle imaginable. This is what we call unpolarized light, which means that all the light waves have different planes of oscillation. Polarized light is when light passes through a filter and the waves of light are limited to one plane of movement and the rest is absorbed, leaving polarized light to only have one plane of oscillation. The filter has tiny gaps in them that are all parallel to one another, as such only waves oscillating in parallel to the filter will pass through. This will decrease the intensity of the light passing through (intensity being the amount of light present), decreasing it dependant on the angle of the filter and if the light is polarised beforehand.

Most questions will ask you to calculate the intensity of the light wave after it has passed through one of these filters, which can be done by multiplying the original intensity by the cos of the angle the filter from perpendicular to the floor. The formula for this is provided in the formula booklet, with the new and original intensity denoted by I and I₀ respectively.