Chapter 32, Problem 32.37P

The sun emits energy in the form of electromagnetic waves at a rate of 3.9 × 10²⁶ W. This energy is produced by nuclear reactions deep in the sun’s interior. (a) Find the intensity of electromagnetic radiation and the radiation pressure on an absorbing object at the surface of the sun (radius r = R = 6.96 × 10⁵ km) and at r = R/2, in the sun’s interior. Ignore any scattering of the waves as they move radially outward from the center of the sun. Compare to the values given in Section 32.4 for sunlight just before it enters the earth’s atmosphere. (b) The gas pressure at the sun’s surface is about 1.0 × 10⁴ Pa; at r = R/2, the gas pressure is calculated from solar models to be about 4.7 × 10¹³ Pa. Comparing with your results in part (a), would you expect that radiation pressure is an important factor in determining the structure of the sun? Why or why not?