Rayleigh scattering

What is Rayleigh scattering

Matter and radiation interact in a variety of ways. The sky is blue because air molecules scatter light, and they scatter light of shorter wavelengths more strongly. Since blue light has the shortest wavelength (in the visible spectrum), it is scattered the most and the sky appears blue. This is called Rayleigh scattering. But clouds are white because of Mie scattering, which is due to light scattered by larger particles like water droplets.

Another form of interaction is fluorescence

when an object absorbs some light of higher energy (like blue colour) and releases it at lower energy (like red colour). It usually happens when an electron absorbs a photon, or a particle of light, jumps to a higher energy level, before releasing that energy and jumping back down. In this process, the electron’s spin must not change. If its spin changes, the process is called phosphorescence.

Fluorescence has many applications. The fluorescent lamp uses an electric discharge to bombard a material with UV light. The material absorbs it and re-emits it as visible light. More curiously, scientists have been finding that the bodies of many mammals also fluoresce. A recent study reported that the bodies of animals belonging to all the known mammalian ordersfluoresced in some way. Some 107 species also had fur that fluoresced. The reason for this ability remains a mystery.

(courtesy:The Hindu)