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Focal length: cm-1?

  1. Feb 25, 2008 #1
    I am doing an assignment for school about the focal length of a concave mirror.
    I found that the focal length for the mirror was 0.0759cm-1
    But, how much is that really in terms of cm? So basically, 0.0759cm-1 = ?cm

    Thanks ;D
  2. jcsd
  3. Feb 25, 2008 #2

    Doc Al

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    Staff: Mentor

    Focal length has units of length, not inverse length. What you probably found was 1/f, not f. Check over your equations and see if that's the problem.
  4. Feb 25, 2008 #3
    Hmm, so if that is 1/f then f would be the inverse of that?
    So it would be 0.0759cm? =o
  5. Feb 25, 2008 #4

    Doc Al

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    Staff: Mentor

    No. If 1/f = 0.0759 cm-1, then f = 1/0.0759 cm.
  6. Feb 25, 2008 #5
    Oh, right :redface:

    So, 1/0.0759 = 13.18cm

    Sorry for my dumb questions, but it's the first time I'm doing this so I'm pretty much confused :blushing:
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