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Photograhing our mirror image

  1. Oct 31, 2010 #1
    If I wish to take a picture of your image while standing 5 m in front of a
    plane mirror, for what distance should I set your camera to provide the
    sharpest focus.

    I guessed the answer would be 10m (distance of object+distance of image). But i don't know why the focus of camera would be sharpest at that distance?
  2. jcsd
  3. Oct 31, 2010 #2


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    Staff: Mentor

    The light that that enters the camera lens diverges from the image point, exactly as if you removed the mirror and placed the object at that location. The light rays travel exactly the same paths just before they enter the camera, in both cases.
  4. Oct 31, 2010 #3
    Could you please explain this further
  5. Oct 31, 2010 #4


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    Science Advisor
    Gold Member

    Have a look at this
    http://www.physicsclassroom.com/class/refln/u13l2b.cfm" [Broken]
    Last edited by a moderator: May 5, 2017
  6. Oct 31, 2010 #5


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    Gold Member

    Simply put: a mirror will reflect the rays from an object to the camera; but it does not change the total distance. The total distance from object to camera is 10m, thus the camera wants to focus at 10m.

    Draw a picture.
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