1. Assume that the sun is a sphere of radius 6.96*10^8 m and that its surface temperature is 5.8*10^3 K. If the sun radiates at a rate of 3.90*10^26 W and is a perfect emitter, at what rate is energy emitted per square meter at the sun's surface?

2. A blue super giant star has a radius of 7.0*10^10 m. The spherical surface behaves as a blackbody radiator. If the surface temperature is 2.2*10^4 K, what is the rate at which energy is radiated from the star?

3. A person steps out of the shower and dries off. The person's skin with an emissivity of 0.70 has a total area of 1.2 m^2 and a temperature of 33 °C. What is the net rate at which energy is lost to the room through radiation by the naked person if the room temperature is 24 °C?

4. The power radiated by a distant star is 4.2*10^27 W. The radius of the star, which may be considered a perfect radiator, is 1.06*10^10 m. Determine the surface temperature of the star.

5. How much energy is radiated by the  object below in ten minutes?


      H = esAT

Absorption and Emission of  Radiation

Energy out = Energy in  Emitted energy/Incident energy = Emissivity = e.

6.  How much does the human body radiate?

Calculating the Sun's Temperature

7.. What is the Sun's temperature?  (Assume the Sun's emissivity is 1.)
If object at temperature T is surrounded by an environment at temperature T0, the net heat flow is:

H(net) = esA [T^4 - T0^4]

8. Standing outdoors on hot August day,Calculate the net heat flow?

9. Standing outdoors on a cold February morning,Calculate the net heat flow?