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: Spectral radiant exitance when given temperature

  1. Jan 25, 2013 #1
    1. The problem statement, all variables and given/known data

    Calculate the spectral radiant exitance for a 10um black body at the following temperatures: -12.0°C, 0°C, 12°C, 1600 K, and 2500 K

    wavelength = 10um
    temperature = see above

    2. Relevant equations

    Planck's equation I think

    3. The attempt at a solution

    No idea. I can't figure out the equation (I am a major noob at this). The given equation is:

    Mλ = C1 / (λ5 [e(C2/λT) - 1)

    λ = wavelength in micrometres
    T = temperature in Kelvin

    C1 and C2 are supposed to be Planck's constants. What does the "e" mean?
  2. jcsd
  3. Jan 25, 2013 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    WOW, okay, you are missing some fundamental math background here. Have you had a course in calculus yet?

    Try reading through these articles:

  4. Jan 27, 2013 #3
    Nope, lol. It's for a geography class.

    I assume the e means 2.71828 then?
    Last edited by a moderator: Jan 27, 2013
  5. Jan 27, 2013 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yeah. Did you read those articles (or at least the intros for each one)? The Planck function includes an exponential function (which is e to the power of some variable).
  6. Feb 1, 2013 #5
    I read the intros, yes. I think I just need an example of this equation done for me. The teacher of my class didn't really give us one.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook