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Converging Lens Magnification Problem

  1. Aug 25, 2004 #1
    What am I missing here?

    A person looks at a gem using a converging lens with a focal length of 15.0 cm. The lens forms a virtual image 26.0 cm from the lens. Determine the magnification.

    (1/p)+(1/q) = (1/f)
    q=26 cm
    f=15 cm

    (1/15)-(1/26)= Ans^-1 = 35.5 cm (p)

    Magnification= -(q/p)
    M= -(26/35.5)
    M= -0.733

    Answer [-.733] has been marked wrong. What did I do?
  2. jcsd
  3. Aug 25, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    check your sign convention

    Your sign convention is incorrect. "q" for a virtual image is negative.

    Welcome to PF, by the way.
  4. Aug 25, 2004 #3
    whoa thanks

    i apologize, i knew that...just dumb tonight

    thanks for the welcome
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