# Why does particle size affect EM radiation scattering

It is my understanding that electromagnetic radiation is absorbed by an electron and then emitted at another angle. So why does particle size affect scattering when the phenomenon involves electrons? Also, why does the size of the wavelength of the light relative to the diameter of the particle matter?

Simon Bridge
Homework Helper
For fundamental particles it doesn't.
What matters is the impact parameter and the cross-section for the interaction.

Are you thinking of things like dust? eg. Rayleigh scattering?

In that case it is a diffraction effect - you need the barrier to be of the same order as the wavelength to get noticeable interference.

For non-fundamental particles, when light (electromagnetic beam) hits the particle, the beam diffracts at a certain angle and intensity, dependent on particle size. This is the basis of particle size measurements, and you can find more information about it on the following link

http://www.quantachrome.co.uk/en/laser-diffraction.asp