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: Diffraction grating and red light

  1. Nov 17, 2008 #1
    1. The problem statement, all variables and given/known data
    White light is spread out into its spectral
    components by a diffraction grating.
    If the grating has 2469 lines/cm, at what
    angle does red light of wavelength 635 nm
    appear in first order?
    Answer in units of ◦.

    2. Relevant equations

    sin(theta) = m([tex]\lambda[/tex] /d)

    3. The attempt at a solution

    theta = inverse sin [( 1 * 635 e-9 m) / 24.69 m} = 1.4735 e -6 degrees
  2. jcsd
  3. Nov 17, 2008 #2


    User Avatar
    Homework Helper

    Hi Kris1120,

    In your formula, d is the distance between grating lines. If there are 2469 lines in every cm, what is the distance between each line?
  4. Nov 17, 2008 #3
    I see... its 1 / 2469 cm! Thank you!
  5. Nov 17, 2008 #4


    User Avatar
    Homework Helper

    That's right (as long as you meant (1/2469) cm; some people inadverdently put the cm in the denominator for this type of problem).

    Glad to help!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook