Temp of Blackbody

1. 1
 
 
 
 
 
 
Find the temperature of a
blackbody if its spectrum
has its peak at
700
,
3
,
3
.
m
m
m
a nm
visible
b cm
microwave region and
c m
FM radio waves






Solution

2. 2
3
3
According to Wien displacement
law for a blackbody:
2.90 10 .
2.90 10 .
m
m
T m K
m K
T




 

 
3 3
9
3 9 6
4 3
( )
2.90 10 . 2.90 10 .
700 700 10
2.90 10 10 2.90 10
700 700
2.90 10 29 10
7 7
29000
4142.86
7
a
m K m K
T
nm X m
X X K X K
X K X K
K
K
 


 
 
 
 
 

3. 3
3 3
2
3 2 1
3
1 2
( )
2.90 10 . 2.90 10 .
3 3 10
2.90 10 10 2.90 10
3 3
290 10 290 29
3 3000 300
0.097 0.97 10 9.7 10
b
m K m K
T
cm X m
X X K X K
X K K K
K X K X K
 

 

 
 
 
 
  
  
3 3
4
4
5 6
( )
2.90 10 . 2.90 10
3 3
29 10 29
9.67 10
3 30000
96.7 10 967 10
c
m K K
T
m
X K K
X K
X K X K
 


 
 
 
  
 