1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    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


    User Avatar
    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.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook