1
ρ
(
λ
,
T
)
d
λ
=
C
2
λ
–
5
e
x
p
(
–
C
1
/
λ
T
)
d
λ
ρ
(
λ
,
T
)
d
λ
=
C
2
λ
–
5
e
x
p
(
–
C
1
/
λ
T
)
d
λ