(a) A small body with temperature T and emissivity E is placed in a large evacuated cavity with...

(a) A small body with temperature T and emissivity E is placed in a large evacuated cavity with interior walls kept at temperature Tw. When Tw – T is small, show that the rate of heat transfer by radiation is

(b) If the body remains at constant pressure, show that the time for the temperature of the body to change from TI to T2 is given by

(c) Two small blackened spheres of identical size, one of copper and the other of aluminum, are suspended by silk threads within a large hole in a block of melting ice. It is found that it takes 10min for the temperature of the aluminum to drop from 276 to 274 K, and 14.2min for the copper to drop the same interval of temperature. What is the ratio of specific heats of aluminum and copper? (The