U4AOS1 Topic 16: Polarisation

Polarisation happens due to a filter that blocks all light, except light that oscillates in the same direction as the slits in the filter.

Note: Only transverse waves can be polarised.

If the filter starts in a position where all the light is able to pass through it and slowly turns.

Once the filter has turned $90 \degree$ all of the light will blocked.

The reason the light is blocked when the slits are horizontal is because the light itself is travelling perpendicular to the direction of its motion.

It's like trying to go through a door. If you walk toward the door normally you will pass through it. But it you're hovering in the air perpendicular to the door your legs and head will probably hit the walls.

Polarising filters come in handy when coherent light is needed. An example of coherent light is with LASERs.

Use the simulation below to see how it works

Created with GeoGebra®, by Tom Walsh, Link