A solid sphere and a hollow sphere of the same material and of equal radii are heated to the same temperature.

Options

A. in the beginning both will emit equal amount of radiation per unit time
B. In the beginning both will absorb equal amount of radiation per unit time
C. Both spheres will have same rate of fall of temeperature `((dT)/(dt))`
D. Both sphere will have equal temperatures at any moment.

Answer

A, B

Explanation

`P_(emitte)=sigmaeAT^4`
since `T_1=T_2`
`P_(absorb)=sigmaeAT_S^4`
So `P_1=P_2` at `t=0`
cooling rate `(-(dT)/(dt))=(sigmaeA)/(mS)[T^4-T_S^4]`
Since `M_HltM_S`, so cooling rate will be different. As cooling rate is not same. So both will ont have same temp at any instant t (except`t=0`).