 
Summary: Physics 408  Exam 2 Name__________________________________________
You are graded on your work, with partial credit where it is deserved.
Please give clear, wellorganized solutions.
h = 6.63 x i0 J s [Planck's constant] k = 1.38 X 1023 J/K [Boltzmann constant]
= 5.67 X 108
m2K4
[StefanBoltzmann constant] c = 3.OOx 108 rn/s [speed of light]
E jii/kT
e / ±1
1. The distance between the Earth and the Sun is R = 1.50 X 1011 m, and the radius of the Sun is
r = 6.96 x 108 m . The radiant energy flux (or intensity) of sunlight at the position of the Earth is
S = solar constant = 1.36 x i03 .
(a) (9) Calculate the total rate of energy generation of the Sun in J/s
(b) (9) Recalling the StefanBoltzmann law, energy flux from perfect blackbody = B T4, calculate the temperature at
the surface of the Sun.
(c) (9) The solar spectrum peaks at about 518 nm, or 518 x io9 m. According to the Wien displacement law, with the
Planck distribution written in terms of the wavelength A,
A
hc
peak
