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Two uniform solid spheres `A` and `B` of same material, painted completely black and placed in free space separately. Their radii are `R` and `2R` respectively and the domainating wavelengths in their spectrum are observed to be in the ratio `1:2`, which of the following is not correct.A. Ratio of their rates of heat loss is `4:1`B. Ratio of their rates of cooling is `32:1`C. Ratio of their temperatures is `2:1`D. Ratio of their emissive powers is `4:1` |
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Answer» Correct Answer - D `lamda_(1)T_(1)=lamda_(2)T_(2)` `(T_(1))/(T_(2))=(lamda_(2))/(lamda_(1))=2` Rate of heat loss `dotQ=4pir^(2)sigma eT^(4)` `(dotQ_(1))/(dotQ_(2))=((r_(1))/(r_(2)))^(2)((T_(1))/(T_(2)))^(4)=4` `dotQ=-ms(d theta)/(dt)=-4/3pir^(3) rho s(d theta)/(dt)` `(((d theta)/(dt))_(1))/(((d theta)/(dt))_(2))=((dotQ_(1))/(dotQ_(2))).((r_(2))/(r_(1)))^(3)=32` |
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