# In a dark room with ambient emperatureT', a black body is kept at a temperature T. Keeping the temperature of the black body constant (at T), sunrays are allowed to fall on the black body through a hole in the roof of the dark room. Assuming that there is no change in the ambient temperature of the room, which of the following statement(s) is/are correct?A. The quantity of radiation absorbed by the black body in unit time will increase.B. Since emissivity=absorptivity, hence the quantity of radiation emitted by the black body in unit time will increase.C. Black body radiates more energy in unit time in the visible spectrum.D. The reflected energy in unit time by the black body remains constant.The answer is A,B,C,D.This question appeared in the last year JEE paper.Can someone explain the answer to me?

Ronak Bothra
7 Points
5 years ago
I think A and D are correct

A) After opening the hole in the roof greater amount of heat is falling on the black body so it will absorb greater amount of heat;

B) Radiations emitted by black body just depends on temperature of black body, so there will be no change in radiation emitted.

C) Again since radiation spectra of black body just depends on temperature of black body so there will be no change in radiation spectra of black body

D) Black body do not reflect anything so there will be no change in radiations reflected.