•
•Hot
objects glow (emit light)
–Heat (and collisions) in material causes electrons to
jump to high energy orbits
–As electrons drop back down, some of energy is
emitted as light.
–
•Reason for name “Black Body
Radiation”
–In a “solid” body the close packing of
the atoms means than the electron orbits are complicated, and virtually all energy
orbits are allowed. So all wavelengths of light can be emitted or absorbed. (In a gas with isolated atoms, only certain orbits are permitted so only
certain wavelengths can be absorbed
or emitted.)
–
–A black
material is one which readily absorbs all wavelengths of light. These turn out to be the same materials which also
readily emit all wavelengths
when hot.
–