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Homework Help: Lenses- magnification adn focal length

  1. May 6, 2010 #1
    1. The problem statement, all variables and given/known data
    Hey,,
    I was wondering if anyone could help me with some physics work i am doing as i am completly stuck.
    Is there supposed to be any relationship with the magnification and focal length of lenses and if so what is it?
    I did an experiment and measure the magnification of lenses different distances from the lenses and also calculated the focal length at these points. Now i am stuck on how to write all this up and what graphs to draw.
    Any help would be much appreciated :s
    xxx


    2. Relevant equations

    I used 1/v-1/u=1/f for focal length
    and size of image/ size of object for magnification

    3. The attempt at a solution
     
  2. jcsd
  3. May 6, 2010 #2

    tiny-tim

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    Welcome to PF!

    Hi PhysicsChick8! Welcome to PF! :smile:

    See the PF Library entry on lens :wink:
     
  4. May 6, 2010 #3
    thanks i read that but i'm kinda very bad at physics and need it explained in very simple terms if possible without too many confusing equations xx
     
  5. May 6, 2010 #4

    tiny-tim

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    As the Library says …

    The image is magnified (with respect to the size of the object) by the factor m = -di/do

    and …

    do is positive for a real object and negative for a virtual object (See Images section).
    di is positive for a real image and negative for a virtual image (See Images section).

    and …

    For the common situation where the object and image are real (do and di both positive), the magnification is negative indicating an inverted image with respect to the object.
     
  6. May 6, 2010 #5
    so if i were plotting stuff on a graph what would i plot? x
     
  7. May 6, 2010 #6

    tiny-tim

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    Well, what are you trying to show? :smile:
     
  8. May 6, 2010 #7
    thats the problem i don't know,,, we had to choose an experiment and i choose the magnification and power of lenses as it seemed easy. Now i have to write it up and draw graphs but im not sure what of as i don't really know what is linked. I really am useless at this if you haven't guessed already x
     
  9. May 6, 2010 #8

    tiny-tim

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    I suppose the obvious graphs would be di against do, and m (= -di/do) against do.

    Try drawing them, and see what you get. :smile:
     
  10. May 6, 2010 #9
    thank you :D x
     
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