Question

How does colour of scattered light depend on the size of the scattering particle?

Answer 1

1. Scattering of light is the process by which light gets deflected and diffused all over as a result of its interplay with tiny matter particles.
2. It is observed that the colour of the scattered light depends on the size of the scattering particles. Here, the following two situations are important:
   1. If the size 'a' of scattering particles is much smaller than the wavelength 'λ' of light falling on the scattering particles (a << λ), the light of shorter wavelengths is scattered much more than light of longer wavelengths. A British Physicist Lord Rayleigh gave a scattering law, according to which the amount (intensity) of scattered light from fine scattering particles is inversely proportional to the fourth power of wavelength of light. Mathematically, $Theintensityofscatteredlight\propto \frac{1}{{(Wavelengthoflight)}^4}$
   2. If the size 'a' of scattering particles is much larger (e.g., dust particles and tiny droplets suspended in air, colloidal solutions) than the wavelength 'λ' of light, they scatter light of all wavelengths almost uniformly, and then the scattered light appears as white.