Theory of the Fireball

with C = 14.
and find
On this basis we calculate the outer radius R of the warm layer
2
Using (6.17) we can then calculate €$/Rae We give t'nis quantity in the
second last line of Table IX. In Yne last line, we nave given the mate-
rial thickness of the warm layer, in relative units,
L' = p2 - R2 - R1
'a Ra
It is seen from the table that R increases only sluwly; the main
2
change in R - R1 at later times is therefore due to the decrease of R
2 I'
The material thickness L' first decreases very slightly; this continues
about as long as R increases, and is due to the fact that about the same
1
mass of warm material gets distributed over a larger area. Later on, L'
increases while R decreases. Until x = 2.5 the chaage of L' remains
1
less than lo%, and after x = 2.5 the calculation is probably meaningless
because the bomb debris comes into view. Therefore, we 'may assume L'
constant, and thus the optical mass slbsorption coefficient (in cm 2 /gm)
at the radiating layer will also be constant. In contrast with this
79
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