Question

the bulb in the rear lamp gives out white light. white light is a mixture of all the colours of light.
the plastic cover acts as a red filter. red light passes through the filter. what happens to the other colours that do not pass through?

Answer 1

If you pass white light through a red filter, then red light comes out the other side. This is because the red filter only allows red light through. The other colours (wavelengths) of the spectrum are absorbed. Similarly, a green filter only allows green light through.