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Homework Help: Ray tracing concave mirror

  1. Nov 27, 2014 #1
    1. The problem statement, all variables and given/known data
    mirrorq.png
    B) Using the mirror equation, find the image distance.

    2. Relevant equations
    1/do + 1/di = 1/f

    3. The attempt at a solution
    mirrorrays.png

    B)
    do = 2cm f = 4cm
    1/do + 1/di = 1/f
    1/di = 1/f - 1/do
    1/di = do/f(do) - f/f(do)
    1/di = (do-f)/(f*do)
    di = (f*do)/(do-f) = (4cm * 2cm)/(2cm - 4cm) = (8cm^2)/(-2cm) = -4cm
    di = -4cm

     
  2. jcsd
  3. Nov 27, 2014 #2
    is it ok that my image distance came out negative? if i am correct this is fine if the image is behind the mirror
     
  4. Nov 28, 2014 #3

    ehild

    User Avatar
    Homework Helper

    It is correct, the distance of a virtual image is negative in the frame of sign convention you applied.
     
  5. Nov 28, 2014 #4
    thank you!
     
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