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!

B Math in the thin lens equation

  1. Jun 2, 2016 #1
    Why isn't 1/f=1/do+1/di just the mathematical equivalent to f=do+di? Can't you raise all terms in the equation to the power of negative 1 to get the latter equation? The maths of reciprocals is confusing me lol.
     
  2. jcsd
  3. Jun 2, 2016 #2
    That is not the lens eqn.
    The lens equation is :- 1/f = 1/v - 1/u
    Where v:- image distance with sign convention
    u:- object distance with sign convention
    just take reciprocal of whole eqn

    ## \frac {1}{\frac{1}{f}} = \frac {1}{\frac{1}{v} - \frac{1}{u}} ##

    ## f = \frac{1}{\frac{(u-v)}{uv}} ##

    ## f= \frac{uv}{u-v} ##

    Clearly it is self explanatory.
     
  4. Jun 2, 2016 #3
    Kuzon has written a perfectly acceptable version of the lens equation, one that is commonly used.

    Kuzon: raising to a power does not follow a distributive law as does multiplication. So we have a(b + c) = ab + ac but (b + c)2 ≠ b2 + c2.
     
  5. Jun 2, 2016 #4
    Sorry, I did not know that version of lens equation; as in our country the lens equation version used is different.
     
  6. Jun 2, 2016 #5
    I have acquired the same as @Sahil Kukreja . The relation is about their reciprocals, and cannot directly be changed to what @Kuzon wrote.
     
  7. Jun 2, 2016 #6
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Math in the thin lens equation
  1. Thin-lens equation (Replies: 2)

  2. Thin lens formula (Replies: 11)

  3. Thin lens (Replies: 3)

Loading...