504 / 1224
=
)ˆ
,
,
(
,
ˆ
E
rE
The net flow of photons through a
phase space cell equals:
ˆ
photons scattered in it
from all others (E’, Ω’)
)
ˆ
, ,
(
E
r scat
q
The basic equation is the LBTE
Let
be the angular fluence (dΦ/dΩdE=dN/dAdΩdE) denoting the number
of photons in phase space element , i.e. passing through a voxel of area dA
normal to located at
,
with wιthin Ω and Ω+dΩ and E between E and E+dE.
At any part of this “phase space”, conservation of E dictates particle density balance.
)
ˆ, ,
( ,
ErE
)
ˆ
,
,(
Er
ˆ
+ photons emitted by a source
in it
)
(
4
)ˆ, (
pr r
E
p
q
−
+
-
photons absorbed or
scattered out of it
)
ˆ,
,
(
,
) ,(
−
Er
E E
rt
L.B.T.E.
r
ˆ