Question

Two spheres of equal masses , one made up of lead and the other of copper have identical surface finish. If these two are heated upto the same temperature $\theta$ and allowed to cool in the surrounding temperature ${\theta }_0$, then the total amount of heat loss during the same time will be

• A. same for both the spheres.
• B. more for the lead sphere.
• C. more for the copper sphere.
• D. nothing can be predicted.

Answer 1

The correct option is C more for the copper sphere.

Since both bodies have the same mass, and same surface that emit radiation.
The amount radiated would only depend on the surface area of the emitting surface.
Since bodies have the same mass, the one with lesser density would have a larger radius and hence larger surface area(emitting surface).
We know that copper has a much lesser density than lead, hence the copper ball would have higher surface area and would emit much more radiation.