Two polarisers

HOW

1. Observe the surroundings through the first polariser by turning the knob.
2. Position the second polariser to observe the surroundings through both devices.
3. By turning the first one, observe the changes in transparency.
4. When the image is dimmed, place a transparent piece of plastic between the polarisers and look at the surroundings through such an optical system.

WHY

Light can act as a wave or as a particle. In this experiment, you observe wave optics.

When the wave vibrations are within one plane, we deal with polarised light. Natural light, which has different vibration planes, can achieve this state by passing through a single polariser.

When the polarisers are set so that they transmit the same polarised light, the image is bright. And when you turn one of the polarisers so that the polarisation planes are perpendicular, the image becomes dimmed. In contrast, the transparent plastic rotates the plane of vibration of a light wave and some light again passes through such a system. This degree of polarisation rotation varies depending on the colour – hence the colours appear.