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Thermal Physics

Blazing goIITian

Joined:	26 Oct 2007
Post:	1018

25 Jan 2008 21:35:13 IST

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431

Radiation

None

A metal foil block is warmed by radiation with a sphere at temperature T and distance d. The power received by foil is P.

If temp and distance both are doubled, the power received will be:

Please show in detail, how you got the answer.

Thanks

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abhishek sinha

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Joined: 18 Dec 2007

Posts: 926

25 Jan 2008 22:04:29 IST

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T^4 / d^2

so 4 times

U V

Blazing goIITian

Joined: 26 Oct 2007

Posts: 1018

25 Jan 2008 22:53:44 IST

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feynmann

Your answer is right, 4 times.

But, please explain ...

abhishek sinha

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Joined: 18 Dec 2007

Posts: 926

25 Jan 2008 22:56:17 IST

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according to Stefan's law E

T^4

again according to the law of intensity P

1/d^2 ( inverse square law )

kundan a.k.a Juan Dankh

Blazing goIITian

Joined: 22 Dec 2007

Posts: 550

25 Jan 2008 23:01:31 IST

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@ UTSAV .......
if you are asking mathematically solving.........
initial P = T^4/d^2

final p = 16T^4/4d^2
thus
4(T^4/d^2)
hence 4 times

U V

Blazing goIITian

Joined: 26 Oct 2007

Posts: 1018

26 Jan 2008 12:45:03 IST

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Thanks, I got it.

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