First slide
Radiation
Question

If a solid sphere and a hollow sphere of the same material and radius are heated to the same temperature:
(i) both will emit equal amount of radiation per sec in the beginning
(ii) both will absorb equal amount of radiation per sec in the beginning
(iii) the initial rate of cooling will be same for both the spheres
(iv) the two spheres will have same temperature at any instant

Easy
Solution

when the body cools only by radiation the rate of cooling is independent of mass 

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