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Lens Radius and Image Size?

  1. Oct 2, 2014 #1
    So for BiConvex Lenses, increasing the lens radius (by making the lens fatter) brings the image and focus closer to the lens, thus making it smaller given constant object position. As demonstrated in this demo
    http://micro.magnet.fsu.edu/primer/java/lenses/lensvariations/index.html


    Yet for the eye, when we want to focus on closer objects, the ciliary muscles contract to fatten the lens and that makes the image larger, not smaller? As demonstrated in this demo: http://micro.magnet.fsu.edu/primer/java/humanvision/accommodation/index.html

    Why are they conflicting? Are they different lenses?

    And while we're on the subject, increasing the refractive index of a lens definitely causes the image to focus closer to the lens right?
     
  2. jcsd
  3. Oct 2, 2014 #2

    TheDemx27

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    Gold Member

    I don't know what you are seeing, but when I increase the lens radius in the first link, the focus moves further away from the lens. This would make it consistent with the second demo.
     
  4. Oct 2, 2014 #3
    Sorry i wasnt clear! When i said radiuss i meant the radiuss that is always double the focal length, not the radius of the glass lens itself.
     
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