thermal physics qa 3/ stefan's law
TRANSCRIPT
© Physics
Helpline
Physics Helpline
L K Satapathy
Thermal Physics 3
Stefan’s Law&
Wien’s Displacement Law
© Physics
Helpline
Physics Helpline
L K Satapathy
Thermal Physics 3
Question : Two spherical stars A and B emit black body radiation. The radius of A is 400 times that of B and A emits times the power emitted from B . The ratio of their wave lengths at which the peaks occur in their respective radiation curves is
(a) 2 (b) 3 (c) 4 (d) 6
A B &A B
410
Answer :
Stefan’s Law :
Power radiated by a spherical star / unit area of its surface is 4E T
[ Where Temperature of the star = T & Stefan’s constant = ]
Total Power radiated by the star is given by 4P E A AT
[ Where surface area of the star = A ]
If radius of the star = R , then 2 2 44 4A R P R T
© Physics
Helpline
Physics Helpline
L K Satapathy
Thermal Physics 3
4 4
4
10 120 2
A A
B B
T TT T
2 [ ]A B
B A
TT
Ans
Correct option = (a)
2 4
A A A
B B B
P R TP R T
For stars A & B: 2 4 2 44 & 4A A A B B BP R T P R T
Again from Wien’s Law , we have .T = constant
4
4 210 400 A
B
TT
© Physics
Helpline
Physics Helpline
L K Satapathy
For More details: www.physics-helpline.com
Subscribe our channel: youtube.com/physics-helpline
Follow us on Facebook and Twitter:facebook.com/physics-helplinetwitter.com/physics-helpline