# Course:ENPH257/Archive/2017St1/Assignments/03

### Assignment #3 for marking

1. Use Planck’s Law to calculate the spectrum and intensity of solar radiation incident on the Earth (actually the top of the Earth’s atmosphere to avoid tangling with the troposphere). Start with the surface temperature of the Sun and its mean distance from the Earth.
a. Plot the intensity spectrum in W/m3 as a function of wavelength.
b. What is the total intensity in W/m2?
c. What is the peak wavelength?

2. A matt black solid aluminum sphere radius 10 cm is placed on a thin pole in the middle of a big, flat open field on a bright sunny windless day. The air and ground temperature is 20 C, but the sky temperature is -20 C. Write some code to predict how the temperature of the sphere will rise under a solar intensity of 1 kW/m2. Assume equilibrium temperature will be attained before conditions change. Create a plot of temperature vs. time.

Make sure that you indicate your answers appropriately, e.g. "The RMS velocity of air at 273K is v_rms = ... ".