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: Focal length corrective lens

  1. Oct 17, 2011 #1
    1. The problem statement, all variables and given/known data

    A person had a near point of 80 cm. What focal length lens would be required to correct this persons near point to 30cm, allowing then to read at this distance

    2. Relevant equations

    Maybe: 1/di + 1/do = 1/f = P
    I found another similar question which used 1/(the given near point aka the 80cm) - 1/(the desired near point aka 30) = 1/f
    This got me the right answer, but I still dont understand why.

    3. The attempt at a solution

    The answer is 48cm
    Last edited: Oct 17, 2011
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted