Polarised Light

A large red and blue cube frame that has orange and blue information panels hanging from top to bottom. Inbetween these panels are blue and orange trianguular and square objects.

Polarising filters can be used to block or transfer light waves at different angles.

How it works

Overlap frames containing polarising filters to see how light is blocked.

Things to try or ask around the exhibit

  • Hold up two polaroid filters, one behind the other. Look through both filters. What do you see?
  • Rotate the filters. What do you notice now?

Background

Light waves vibrate up and down, from side to side and at all angles. This is unpolarised light. Polaroid filters in sunglasses reduce glare by only allowing light waves that vibrate in one direction to pass through. When you hold the front and back polaroid filters the same way, light waves that vibrate up and down (vertically) will pass through both filters, so you see some light.

The back filter allows only ‘vertical’ light waves to pass through and blocks light waves vibrating in other directions. If you turn the front filter around (same as the picture below), it will block the vertical waves and you will see less light.

Finding the science in your world

Polaroid sunglasses reduce glare and make people more comfortable outdoors. Polarising filters within the sunglasses block light that reflects at different angles off roads and water surfaces.

Polarising filters are also used by medical researchers and building engineers to detect stress within bones and structures.