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Homework Help: Spectacles, Focal length and Lens Formula

  1. Apr 7, 2010 #1
    1. The problem statement, all variables and given/known data

    When using the lens formula: 1/f = 1/u + 1/v

    for someone who has short sightedness and cannot focus on objects on objects more than 2.5m away, I get:

    1/f = 1/infinity + 1/-2.5
    f = -2.5 m

    If using the formula for someone who had long sightedness and could not focus on objects closer than 2.5m does this mean the equation would be:

    1/f = 1/infinity + 1/2.5
    f = 2.5 m

    Thanks! :smile:

    2. Relevant equations

    1/f = 1/u + 1/v

    3. The attempt at a solution
  2. jcsd
  3. Apr 9, 2010 #2
  4. Apr 11, 2010 #3
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