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Focal length of a convex mirror

  1. Jul 16, 2013 #1
    1. The problem statement, all variables and given/known data

    An object is 12.0 cm in front of a convex mirror. When the convex mirror is replaced
    with a flat mirror, the image distance is 5.0 cm farther away from the mirror. What is the
    focal length of the convex mirror?

    2. Relevant equations



    3. The attempt at a solution



  2. jcsd
  3. Jul 17, 2013 #2


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    How is the image distance related to the object distance in case of a flat mirror?

  4. Jul 17, 2013 #3
    They would be equidistant to the mirror?
  5. Jul 17, 2013 #4


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    Yes. So the mirror image in case of flat mirror is farther away by 5 cm than the image produced by the convex mirror. If the object distance is 12 cm and the image distance is shorter by 5 cm, what can be di?

  6. Jul 17, 2013 #5
    di=12cm for the flat mirror
    di=7cm for the convex mirror?
  7. Jul 17, 2013 #6
    Using the above di, I got f=0.12m.
  8. Jul 17, 2013 #7
    The image is behind the mirror.
  9. Jul 17, 2013 #8


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    The image is at 7 cm distance from the mirror, but the mirror is convex, is the image virtual or real?
    What is the sign of di ?

  10. Jul 17, 2013 #9


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    Have you solved the problem? A quick ray Trace will do it for you.
  11. Jul 18, 2013 #10
    The problem statement tells us that the image is behind the mirror.
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