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, sT (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