Question

The graph, shown in the adjacent figure, shows the fall of temperature (T) of two bodies x and y, having the same surface area, with time (t) due to emission of radiation. Find the correct relation between emissivity power (E) and absorptive power (a) of the two bodies

• A. > ; <
• B. < ; >
• C. > ; >
• D. < ; <

Answer 1

The correct option is C

> ; >

It follows from the figure that the temperature of body x falls more rapidly with time than that of body y. Hence $E_x$ > $E_y$. Also a good emitter of radiation is also a good absorber of radiation (Kirchhoff’s law). Hence $a_x$ > $a_y$. Thus the correct choice is (c)