Two circular disc `A` and `B` with equal radii are blackened. They are heated to same temperature and are cooled under identical conditions. What inference do your draw from their cooling curves?

Options

A. A and B specific heat
B. Specific heat of A is less
C. Specific heat of B is less
D. Nothing can be said

Answer

B

Explanation

When a body cools by radiation, the rate of cooling is given by:
`(d theta)/(dt) = (eAsigma)/(ms) (theta^(4)-theta_(0)^(4))`
`-ve` sign shown that temperature decreases, i.e., the body cools, is the specific heat of materail and `theta_(0)` is teh surrounding temperature
or, `(d theta)/(dt) prop 1/s`
i.e., rate of cooling `(R = d theta//dt)` is inversely proportional to the specific heat of material. for a, rate of cooling is large, therefore, specific heat of `A` is smaller.