So, if matter (an atom) absorbs light (a photon) momentum is transferred to the matter
Light can force atoms to move!
re, the radius of an
electron, giving a cross
section, σT (cm2)
The flux of light, F (ergs s-1 cm-2)
The rate at which momentum is absorbed by the electron
By replacing the cross section of a single electron with the opacity (cm2 g-1), the combined cross section of a gram of plasma, we get the acceleration due to radiation