1. Not finding help here? Sign up for a free 30min 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!

Focal Length of Eye

  1. Apr 16, 2009 #1
    1. The problem statement, all variables and given/known data
    The diagram shows the eye of a person with normal vision looking at an object that is very far away.
    a) Determine the focal length of this persons eye.
    b) Later in this person's life, the focal length will change to between 2.1 cm and 2.3 cm. Will this person suffer from myopia or hyperopia? Explain your answer.
    c) Will this person require a convex or concave lens to correct this problem?

    2. Relevant equations
    Center of curvature= 1/2 diameter
    Focal length= 1/2center of curvature


    3. The attempt at a solution
    a) C=1/2D
    =1/2(2.5cm)
    =1.25cm

    F=1/2C
    =1/2 (1.25)
    =0.625

    It doesn't make sense though, that focal length seems too small/odd. It says in the question that it changes to between 2.1 and 2.3, so my answer seems wayyyyy off...http://img23.imageshack.us/img23/9751/eyecopyw.jpg [Broken]
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 16, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    Focal length= 1/2center of curvature
    This is true for mirrors, not for lens.
    In the above problem f = 2.5 cm.
     
  4. Apr 17, 2009 #3
    Focal Length of 2.5? Wow, that seems...too simple?
     
  5. Apr 17, 2009 #4

    rl.bhat

    User Avatar
    Homework Helper

    When a parallel beam of light falls on a lens , it forms an image at focal point.
     
  6. Apr 19, 2009 #5
    Thanks. Another question though. How would you find the distance in which an object can be seen clearly from by just using the number 2.5 (and possible 2.1 and 2.3)?
     
  7. Apr 20, 2009 #6

    rl.bhat

    User Avatar
    Homework Helper

    Using f as 2.5 cm and di as 2.1 and 2.3, find do. If do is lass than 25 cm,convex lens to be used. And if it is more than 25 cm concave lens to be used. For a healthy eye the object should be at 25 cm to see distinctly.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Focal Length of Eye
  1. Focal Length (Replies: 1)

  2. Focal Length (Replies: 0)

  3. Focal length (Replies: 2)

  4. Focal length (Replies: 1)

Loading...