1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Photons Emitted by the Sun

  1. Oct 7, 2009 #1
    1. The problem statement, all variables and given/known data
    The sun emits 3x1032J of energy every day. Assume it emits only yellow light (6x10-7m wavelength. a. What is the energy of each photon of yellow light? b. How many photons does the sun emit every day?

    2. Relevant equations

    E = hf

    3. The attempt at a solution
    So I think I have question A complete, my solution is the following.
    F = (3x108 m/s)/(6x10-7 m) = 5x1014 Hz
    H = (6.6x10-34Js)
    E=h*f (6.6x10-34Js)(5x1014Hz) = 3.3x10-19 J
    Or E = 2 eV

    But problem B I am stumped. I don't even know where to begin to figure this out. Can anyone help put me in the right direction?
  2. jcsd
  3. Oct 7, 2009 #2


    User Avatar
    Homework Helper
    Gold Member

    You computed the energy of a single photon in J. You have the total energy output of the sun (n photons) in a day also in J. You seem pretty close to an answer.
  4. Oct 10, 2009 #3
    So the answer is 9.9x1013 photons?
  5. Oct 10, 2009 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    If you multiply 3x1032J and 3.3x10-19 J/photon, the result is 9.9x10^13 J2/photon.

    Those units, J2/photon, do not make any sense. So no, that is not it.

    Since the question asks for the number of photons, you're looking for an answer with units of "photons" in it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook