Question

In traffic signals _________ colour light is used to stop vehicles because it has ______ wave length. (Hint: scattering of light is inversely proportional to the fourth power of its wavelength)

Answer 1

In traffic signals red colour light is used to stop vehicles because it has longest wave length.

The scattering is inversely proportionate to the wavelength - longer the wavelength, smaller the scattering, hence it can be easily seen from a very long distance.