Using polarised waves

Thee D images

Two images taken a small distance apart (in the same way as each of your eyes see two images) are projected onto a screen. One is horizontally polarised and the other vertically polarised. The glasses use polaroid filters so that each eye only sees one of the images. The brain interprets this as the image having depth.

Showing how polaroid glasses work when used to see 3D images
Using polaroid glasses to see 3D images

TV aerials

TV and radio signals are polarised because they are transmitted by aerials which are long lengths of wire. The elements of the receiving aerial must be aligned in the same direction (in this case horizontally) to enable a good reception signal. The alignment cuts out any signals which are vertically polarised.

TV aerial with horizontal bars
TV aerial


Light from a blue sky is partly polarised. This is caused by the light exciting the electrons in atmospheric gases. If a polaroid filter is used in front of the camera, the contrast is increased.

Contrasting images to show how a polaroid filter is useful when photographing sky
Photographing sky

Stress analysis

In the design of new engineering pieces which may be put under stress models are used for stress analysis. Some materials, for example perspex rotate the plane of oscillation of light passing through. This varies depending on the stresses imposed and is different for different wavelength i.e. different colours. So instead of seeing white light we may see colours. If we make a model of the new design in perspex we can then apply the forces that it might experience in use and examine the colour of the light passing through.

Using polarised light to analyse the stresses within a perspex model
Using polarised light

The image below is taken of a perspex protractor bent while using polarised light in an arrangement like the one above.

There are more pages on the properties of waves, here: