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: Multiple Lens System(Objectless and Parallel Rays)

  1. Apr 14, 2016 #1
    1. The problem statement, all variables and given/known data
    Consider a telescope composed of two convex lenses, the objective lens and the eyepiece. The objective lens has a focal length of 26cm. Rays parallel to the principle axis enter the telescope through the objective lens and exit the telescope from the eyepiece as parallel rays. If the distance between the two lens is 30cm, find the focal length of the eyepiece.

    2. Relevant equations
    1/f = 1/d(object) +1/d(image)

    3. The attempt at a solution
    I am used to solving questions where rays come from an object and plugging in values. When rays are parallel and doesn't converge, how do I solve such a question? How do I start?

    I know the rays entering the objective lens will converge on the focal point(26cm) since they are parallel rays.

    Is the focal length of the eyepiece 4cm? (30cm-26cm)
  2. jcsd
  3. Apr 14, 2016 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    Hello John, :welcome:

    According to your relevant equation: yes.
    Make a drawing to check this out !
  4. Apr 14, 2016 #3
    Ah- thank you, ByU.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted