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 maker's equation used correctly?

  1. Feb 9, 2012 #1
    1. The problem statement, all variables and given/known data

    An object is placed 60 cm from a thick double convex lens, with faces of radii of curvature 20 cm and 30 cm, with thickness of 2 cm, and index of refraction is 1.5. Find the position of the image. Ans: ( 39.9 cm)

    2. Relevant equations

    lens maker's equation, na/object + na/image = (nb - na)(1/R1 - 1/R2)

    3. The attempt at a solution

    I used this equation and got 40 cm, as opposed to 39.9. I figured it couldn't be a rounding error considering the numbers given. Am I supposed to use the 2 cm thickness somehow?
     
  2. jcsd
  3. Feb 9, 2012 #2
    When I calculated the answer, it came out to be 40.9 cm. Strange!! I used the lensmaker equation given in Wikipedia. These were my results : f= 900/37 cm, u=-60 cm (given) So, using lens formula v = 40.9cm. And yes you need to use the thickness. See the lensmaker's equation in Wikipedia!!!
     
  4. Feb 9, 2012 #3
    @Danny :the equation which you are using seems to be derived from thin lens equation where you neglect thickness as it's too small compared to Radii of curvature.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Lens maker's equation used correctly?
  1. Lens Makers Formula (Replies: 1)

Loading...