A solid metallic sphere of radius 5cm is maintained at a uniform temperature of 800K. Its surface has an emissivity of 0.60. The Stefan–Boltzmann constant may be taken as σ=5.67×10−8W m−2K−4.
a. (i) Calculate the rate at which the sphere loses thermal energy by radiation.
b. (ii) Determine the ratio of the power radiated by this sphere to the power that would be radiated by an ideal blackbody of the same size and temperature.
c. (iii) If the sphere is coated with a matte black paint that increases its emissivity to 0.95, find the percentage increase in its radiative power compared with the original uncoated sphere.