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Convex mirror find object distance

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  1. Mar 17, 2015 #1
    1. The problem statement, all variables and given/known data
    An object is placed in front of a convex mirror with a 45.6-cm radius of curvature. A virtual image half the size of the object is formed. At what distance is the object from the mirror?

    2. Relevant equations
    1/f=1/d0+1/di
    hi/h0=-di/d0

    3. The attempt at a solution
    hi=-1/2h0
    f=45.6/2=22.8

    di=-1/2d0

    1/22.8=1/d0-2/d0
    d0=-22.8

    This is my solution but this is nor correct.....anyone plz tell me the mistake. thanks!
     
  2. jcsd
  3. Mar 17, 2015 #2

    Suraj M

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    Firstly please use brackets, it looks like it may be ##d_i=\frac{-1}{2d_o}##or ##d_i=\frac{-1}{2}d_o##
    and i don't see the need for the -ve sign in the above equation(logically).
    Also because when you substitute the ##h_i## you should negate it as it is inverted, so there shouldn't be a -ve sign for your above equation
     
  4. Mar 17, 2015 #3
    ok so after editing the ans becomes
    1/22.8=1/d0+2/d0
    d0=68.4
     
  5. Mar 18, 2015 #4

    Suraj M

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    I'm sorry i correct myself, i thought it was a concave mirror, so you shouldn't negate ##h_i## as it is erect.
    you were right. The answer you have obtained, looks to be right. Why do you feel it is wrong?
     
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