Properties Of Solids And Liquids Question 463

Question: A spherical black body with a radius of 12 cm radiates 459 W power at 599 K. If the radius were halved and the temperature doubled, the power radiated in watt would be

Options:

A) 225

B) 459

C) 999

D) 1899

Show Answer

Answer:

Correct Answer: D

Solution:

[d] The energy radiated per second by a black body is given by Stefan’s Law Et=σT4×A , where A is the surface area.

Et=σT4×Aπr2(Forasphere,=4πr2)

Dividing (ii) and (i), we get E/t450=(1000)4(0.06)2(500)4(0.12)2=2422=4

Et=450×4=1800W



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