Question

Why is a danger signal light red in colour

Answer 1

When the light passes through atmosphere, it gets scattered by small air particles. The scattering of light is inversely proportional to the fourth power of its wavelength. As the red light has the highest wavelength among all the colours, so it is scattered the least. Due to which most of the light gets reflected back and can travel longer distances through rain, fog, dust etc. to reach our eyes effectively.