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!

Homework Help: Contact lenses, focal length and uncorrected far point distance

  1. Nov 4, 2009 #1
    1. A nearsighted person wears contacts with a focal length of -7.6cm. If this person's far point distance with her glasses is 8.7m, what is her uncorrected far point distance?

    2. 1/F=1/do+1/di

    3. 1/-7.6=1/do+1/870

    I am completely lost here...please help. Thanks!
  2. jcsd
  3. Nov 5, 2009 #2
    Re: Optics

    So it's not just me then...
  4. Nov 5, 2009 #3


    User Avatar
    Science Advisor
    Homework Helper

    Re: Optics

    The image distance is constant in both cases (the length of the eyeball)
    You have an unknown focal length lens (the eye) and a combintion of the same unknown lens and a known lens with a known object distance.

    So write the equations for object, image distance and focal length for both cases.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook