1.

Raed the following passage and and answer the following questions. Stefan's law states that the ernergy emitted per second per unit area of the perfect black body is directly proportional to fourth power of its absolute temperature i.e. EpropT^(4) or E=sigmaT^(4) where sigma is called Stefan's constant. If the body is placed in enclosure maintained at temperature T_(0) then E=sigma(T^(4)-T_(0)^(4)). If temperature difference between the body and the surroundings is very small then energy emitted per second per unit area of the body and surrounding i.e Eprop(T-T_(0)). This is known as Newton's Law of cooling and is a special case of Stefan's Law.Two bodies P and Q are having equal surface areas and are maintained at temperature 17^(@)C and 27^(@)C respectively. Then radiant energy emitted per second are in the ratio of :

Answer»

`16:81`
`8:27`
`2:3`
`7:8`

SOLUTION :`(E_(1))/(E_(2))+(sigmaT_(1)^(4))/(sigmaT_(2)^(4))=((290)/(300))^(4)= 87=7/8`
So correct CHOICE is (d).


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