A thin film of soap will shine with all the colours of the rainbow. But why?

Read more: Soap Film Interference

A convincing demonstration of how fibre-optics work using a stream of water and a laser.

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Read more: Water Fibre-Optic

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Fluorescent rocks absorb ultraviolet light and emit optical light, making them appear to glow in the dark.

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Read more: Fluorescence

When the two polarizers are set 90 degrees to each other, no light passes through.

Read more: How Do Polarizers Work?