Colour Filters

Colour filters work by filtering out specific wavelengths, allowing only certain colours to pass through. Therefore, colour filters absorb all colours except for the filter’s colour, which is transmitted.

  • A primary colour filter only allows one of the three primary colours (red, green or blue) to be transmitted.

For example, if we pass white light through a blue filter:

A diagram illustrating the process of white light passing through a blue filter, resulting in blue light that then reaches a pair of eyes. The white light is shown approaching the blue filter from the left, and only blue light emerges on the other side, directed towards the eyes on the right.

White light contains all different wavelengths of visible light. When white light passes through a blue filter, only the blue light is transmitted, while other colours are absorbed. This results in blue light emerging from the other side and reflecting into our eyes.

An object will appear black if the filter absorbs all the wavelengths of visible light. For example, when green light passes through a blue filter:

A diagram illustrating the process of green light approaching a blue filter from the left. Upon passing through the blue filter, no light emerges, resulting in blackness that then reaches a pair of eyes on the right.

If green light passes through a blue filter, no colour is transmitted, so the light will appear black.

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