•
•Hot
objects glow (emit light) as seen in PREDATOR, SSC Video, etc.
–Heat (and collisions) in material causes electrons to
jump to high energy orbits,
and as electrons drop back down, some of energy is emitted as light.
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•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.
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.
–
•The hotter the material the more energy it
emits as light
–As you heat up a filament or branding iron, it glows
brighter and brighter
•
•The
hotter the material the more readily it emits high energy (blue) photons
–As you heat up a filament or branding iron, it first
glows dull red, then bright
red, then orange, then if you continue, yellow, and eventually blue
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