How is scattering of light related to the wavelength of light and the size of a particle which scatters it, both qualitatively and quantitatively?
1 Answer
More light is scattered when the scattering cross-section of the particles is large.
Explanation:
When the scattering particles are much smaller than the wavelength of light, the scattering is known as Rayleigh scattering.
In this case the scattering cross-section is proportional to
It follows that in this regime light with a shorter wavelength is more greatly scattered than light with a longer wavelength.
When the wavelength of light is much smaller than the scattering particle(s), the collision can be viewed classically as a particle-like photon hitting a screen. The scattering cross-section in this case would be the area of the screen ---- independent of wavelength so long that the screen is much larger than all of the wavelengths considered.
I'm not sure of the general dependence of the cross-section on wavelength when the particle size is comparable to the wavelength of the particle. I suppose it would depend on the size and refractive index of the particles.
However, in the case of water droplets in clouds, the water droplets are of comparable size to the wavelength of visible light and the scattering is described by Mie scattering. Clouds appear white so the scattering would not depend very strongly on wavelength.
