Question

A solid sphere and a hollow sphere made up of the same material and of equal radii, are heated to the same temperature. Then,
(Consider both the sphere, a blackbody)

• A. both will emit equal amount of radiation per unit time in the beginning.
• B. for solid sphere, the rate of emission of heat will be larger.
• C. for hollow sphere, the rate of emission of heat will be larger.
• D. None of the above.

Answer 1

The correct option is A both will emit equal amount of radiation per unit time in the beginning.

From the Stefan-Boltzmann law, the energy of thermal radiation emitted per unit time by a blackbody of surface area $A$, is given by,

$\frac{Q_e}{t}=\sigma A{T}^4$

Here, $\sigma$ is Stefan's constant.

As both the spheres have equal radii and are at the same temperature initially, the rate of emission will be same in the beginning.

Hence, $\left(A\right)$ is the correct answer.