Theory of the Fireball

When this is done in a case of constant ( frequency-independent )
absorption coefficient, the ultraviolet transport will be related to the
visible radiation transport as the respective intensities in the Planck
spectrum. This condition seems to be nearly fulfilled at 12,000°. At
8000°, the absorption in the near ultraviolet (2.75 to 4.2 ev) is about
three tines that in the visible; then the W transport will be one-third
of that corresponding to the Planck intensity. Since the radiating
temperature near the second radiation maximum is between 8000 to 10,OOOo,
the actual W transport will be between one-third and the full Planck
value, relative to the visible radiation. According to (3.36), the W
contains about 43$ ,of the Planck intensity at 8000'; hence the total
radiation transport at this temperature is about
of the black body radiation. At 12,000° we get the full black body value.
For simplicity we have assumed the full black body radiation in Sec. 5, i
even though the W is not emitted to large distances. But this problem
could,. and should, be treated more accurately.
Having discussed the influence of the W on the total radiation flow,
we nuw examine what happens to the W radiation after it has gone through
If
the "radiating layer, i.e., the layer which emits the visible light to
large distances. The very near ultraviolet, 2.75 to 3.5 ev, wiU. be
partially absorbed at 4000 to 6000°, especially if the layer of matter
2
at these intermediate temperatures becomes thick, 0.3 to 0.5 gm/cm or SO.
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43