Two spheres of same material and radii 5 m and 2 m are at temperature 200 K and 250 K respectively. The ratio of energies radiated by them per second…

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Two spheres of same material and radii 5 m and 2 m are at temperature 200 K and 250 K respectively. The ratio of energies radiated by them per second is

MARKS Content Team · Accepted Answer

Correct answer: (A) 64: 25. By Stefan's Law: The formula of power radiated in terms of cross-section area and temperature of the body, P=σeAT^4, here σ is the constant given by Stefans' and e is the emissivity power, P_1P_2=(σeA_1T1^4)/(σeA_2T2^4)=(r1^2T1^4)/(r2^2T2^4)=(5^2200^4)/(2^2250^4)=(25×160000)/(4×625×625)⇒P_1P_2=40000/(25×625)=64/25

Two spheres of same material and radii $5 m$ and $2 m$ are at temperature $200 K$ and $250 K$ respectively. The ratio of energies radiated by them per second is

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