RADIATIVE EQUILIBRIUM 
113 
v' radiation corresponds to the temperature drop in 2 cm. The net outward 
flow for v' is thus only one-hundredth of that of v". 
If v' represents 1 per cent, of the radiation and v" the remaining 99 per 
cent., the absorption-line at v' will double the total amount of absorption 
and emission going on; although constituting but a small part of the 
radiation it does as much business as all the rest put together. This means 
that Jc t is doubled. But as regards opacity the effect is that 1 per cent, of 
the radiation suffers an almost complete check, and the rest flows through 
as before. Hence & 2 is only increased 1 per cent.