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Homework Help: Mirror problem

  1. Apr 28, 2008 #1
    1. The problem statement, all variables and given/known data

    an image in a convex mirror is 12cm tall and 30cm from the mirror.IF the focal length is 50cm, where is the object and how tall.

    2. Relevant equations

    M= hi/ho =-di / do

    3. The attempt at a solution
    i got 7.5cm for the object height but a convex mirror always gives a reduced image?
  2. jcsd
  3. Apr 28, 2008 #2


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    Homework Helper

    Hi myoplex11,

    It's difficult to follow since you did not post the actual numbers that you used.

    However, I think the problem is that you either put in the incorrect image distance, or the incorrect focal length.
  4. Apr 28, 2008 #3
    here is my work:
    (1/do)=1/50 - (-1/30)
    ho= - (18.75/-30)*12 = 7.5
  5. Apr 28, 2008 #4


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    Homework Helper

    Since this is a convex mirror, what do you know about the focal length?
  6. Apr 28, 2008 #5
    i am not sure
  7. Apr 28, 2008 #6
    oh yeah focul length is negative thanks.
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