Problem Set #2

Problem set due in class, Jan 22. Show your work, neatly.

1) What are the peak wavelengths for stars of the following temperatures, what colors do these correspond to (4 points):

  1. 25,000 K (Answer: 1160 Angstroms in the UV)
  2. 7,000 K
  3. 4,000 K
  4. 600 K

2) What is the flux per square meter for the same stars in problem #1? (4 points) (Answer: 2.2x10^10 Watts/m^2 for the 1st one)

3) For the following radii and temperatures, what are the total luminosities of the following stars (remember to convert solar radii into meters)? Compare these numbers to the total luminosity of the Sun (3.9x10^26 Watts) (4 points)

  1. 25,000 K, 10 solar radii (Answer: 1.4x10^31 Watts)
  2. 7,000 K, 1.5 solar radii
  3. 4,000 K, 0.7 solar radii
  4. 600 K, 0.1 solar radii

4) Find the wavelength of the photon emitted in the transition of a hydrogen atom from n2 = 110 to n1 = 109 (4 points) (Answer: 0.06 meters)