Question

Explain why the lights of red colour are used for danger signals.

Answer 1

Light of red colour is always preffered for representing the danger signals. The reason behind this is the least scattering of red colour.
All the colours travel with different speed in a particular medium of a certain refractive index. Their speed varies because of their difference in wavelengths. Similarly, because of their different wavelengths, these colours suffer different levels of scattering by the particles of a particular medium.
The amount of scattering that a colour undergoes is directly dependent on the length of its wavelength - larger the wavelength, smaller the amount of scattering.
Red coloured lights have the longest wavelength among all the colours in the visible spectrum. Hence, it sufferes the least scattering. Due to this, red colour light can travel a large distance and can be spotted by an observer so as to avoid the danger.