Question

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 and absorptivity power of the two bodies

A. `e_(x) gt e_(y) and a_(x) lt a_(y)`
B. `e_(x) lt e_(y) and a_(x) gt a_(y)`
C. `e_(x) gt e_(y) and a_(x) gt a_(y)`
D. `e_(x) lt e_(y) and a_(x) lt a_(y)`

Answer 1

Correct Answer - C
Ratio of cooling `(-dT)/(dt) alpha` emissivity(e)
From graph, `((-dT)/(dt))_(x) gt ((-dT)/(dt))_(y)`
`rArr e_(x)gte_(y)`
Further emissivity `ealpha` absorptive power (a)
`rArr a_(x) gt a_(y)` therefore good absorbers are good emitters)