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Lens - find the focal length

  1. May 3, 2009 #1
    Lens -- find the focal length

    1. An object 3.0 cm tall is placed 20 cm in front of a converging lens. A real image is formed 10 cm from the lens. What is the focal length of the lens?

    2. 1/f = 1/do + 1/di

    3. 1/f = 1/do + 1/di
    1/f = 1/20 + 1/10
    f = 6.667 cm

    I'm not sure if this is right and if you can can you show me how the diagram would look like. Thank You!!
  2. jcsd
  3. May 3, 2009 #2

    Doc Al

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    Last edited by a moderator: Apr 24, 2017
  4. May 3, 2009 #3


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  5. May 3, 2009 #4
    Re: Lens -- find the focal length

    Thank You!!
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