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 Points of a Thick lens

  1. Feb 8, 2012 #1
    1. The problem statement, all variables and given/known data

    A thick lens has an index of refraction of 1.560, thickness of 3.0cm, and radii of curvature of R1= -4.50cm, R2= -3.60cm.

    Calculate the positions of the focal points (relative to the vertices).

    2. Relevant equations

    [itex]\frac{n}{s}+\frac{n'}{s'}=\frac{n'-n}{R}[/itex]

    [itex]ffl = \frac{f1(t + f2)}{t-(f1 + f2)}[/itex]

    3. The attempt at a solution

    I assume I need to first focal length for each lens to plug into the front focal length and back focal length formulas, meaning s' = ∞ so for L1:

    f1 = [itex]\frac{R}{n'-n}=\frac{-4.50cm}{1.560-1.000}[/itex] = -8.04cm

    Do I have the right idea? If so, will I need to swap the indexes of refraction when doing the opposite side of the lens, so that light is coming from the left side?
     
  2. jcsd
  3. Feb 9, 2012 #2
    These might help?

    "For the case of a lens of thickness d in air, and surfaces with radii of curvature R1 and R2, the effective focal length f is given by:"

    From half way down the following page,

    http://www.answers.com/topic/focal-length

    Worked examples here,

    http://www.drdrbill.com/downloads/optics/geometric-optics/Thick_Lenses.pdf

    Found via,

    https://www.google.com/search?hl=en...&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi

    https://www.google.com/webhp?hl=en#...w.,cf.osb&fp=fc8f4a6474bcae3f&biw=917&bih=404

    Good luck!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Focal Points of a Thick lens
  1. Is this the focal point? (Replies: 10)

  2. Lens and focal point (Replies: 1)

  3. Thick lens (Replies: 4)

  4. Focal length of a lens (Replies: 10)

Loading...