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Homework Help: Binoculars, water

  1. Aug 20, 2013 #1
    1. The problem statement, all variables and given/known data
    A type of binoculars used for observing lobsters 10m below the water surface has an ocular with f = 40mm and an objective with f = 200mm (on the side of the air). The objective is a plano-convex lens. The tube is filled with air. What's the distance between the lenses?

    2. Relevant equations
    n_water = 1.33
    n_glass = 1.52

    1/f = 1/s + 1/s'

    [tex]\frac{n_a}{s} + \frac{b}{s'} = \frac{n_b - n_a}{r}[/tex]

    3. The attempt at a solution
    Tried playing around with the lensmaker formula but not getting past the radius which I presume I can get from f = 200mm, but not quite sure how the focal length is affected by the fact that there are several surfaces.
    Last edited: Aug 20, 2013
  2. jcsd
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