Question

In traffic signals ............... colour light is used to stop vehicles because it is having ............... wave length.

Answer 1

In traffic signals red colour light is used to stop vehicles because it is having longer wave length. The colour which is having longer wavelength will undergo lesser scattering, hence it is visible from a longer distance. The primary reason why the colour red is used for danger signals is that red light is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a colour. Therefore blue which has the least wavelength of all the visible radiations is scattered the most and red which has the highest wavelength of all the colours we can see is scattered the least. So red light is able to travel the longest distance through fog, rain, and the alike.