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 equation: pretty simple probably

  1. Jan 8, 2010 #1
    1. The problem statement, all variables and given/known data

    A converging lens ( f = 10.4 cm) is held 8.80 cm in front of a newspaper, the print size of which has a height of 2.04 mm. Find the image distance (in cm) and the height (in mm) of the magnified print.

    D= _____cm
    H= _____cm

    2. Relevant equations


    3. The attempt at a solution


    I know this is the right setup but i feel like an idiot because I forget basic math...I don't remember how to solve this equation so if something can walk me through it step by step that would be great. I only have a simple scientific calculator that I keep using and get a decimal that isn't that right answer so i just don't know
  2. jcsd
  3. Jan 8, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi johnson.3131! :smile:
    Well, there's only two steps …subtract 1/8.80 from 1/10.4, and then 1/x it.

    If you're getting it wrong, perhaps you'd better show us what you've done.

    (you did remember the height is in mm, not cm?)
  4. Jan 8, 2010 #3
    this is correct
    1/10.4 - 1/8.8 = 1/di

    Your calculator should have a 1/x function to calculate the two fractions on the left and subtract the answers. (The answer will be negative).
    Then take that answer and use 1/x on it to get the value of di. (also negative)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Lens equation pretty Date
Deriving Thick lens Equation Mar 10, 2018
Thin lens equation and image formation Apr 21, 2014
Thin Lens Equation: Nearsighted Mar 29, 2014
Lens maker's equation used correctly? Feb 9, 2012