The graph shown in the adjacent diagram, represents the variation of temperature (T) of two bodies, x and y having same surface area, with time (t) due to the emission of radiation. Find the correct relation between the emissivity (e) and absorptivity (a) power of the two bodies. (IIT JEE 2003)
ex>ey,ax>ay
From the graph it is clear that initially both the bodies are at same temperature but after that at any instant temperature of body x is less than the temperature of body y. It means body x emits more heat i.e., emissivity of body x is more than body y ∴ex>ey and according to Kirchhoff's law good emitter are also good absorber so ax>ay.