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Homework Help: Nature of image formed by a plane mirror

  1. Jun 2, 2006 #1
    1) A beam of light incident on a plane mirror forms a real image on reflection. It is said that the incident beam in that case is convergent. Is it true?
    I think it is due to the fact that a plane mirror normally forms virtual images of real object. In order that a real image be formed by it, the object should be virtual and only a convergent beam of light can produce a virtual object. Is my argument right?
    2) What is the nature of the picture seen on the screen of a pin hole camera? Is it an image or a Shadow?
    I think it’s an image. What do you say Sir?
    3) A ray reflected successively from 2 plane mirrors inclined at a certain angle undergoes a deviation of 300 degrees. How many images are observable?
    I solved it in the following way:
    We know that the deviation produced by 2 plane mirrors inclined at an angle y is 180 + 2y.
    Therefore 180 + 2y = 300
    y = 60
    Here it is assumed that the object is placed symmetrically between the 2 inclined mirrors. We know that number of images observed = (360/y) – 1
    = 5
    Is it right?
  2. jcsd
  3. Jun 3, 2006 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    The rays from an object always diverge. The plane mirror does not change the divergence - they just reflect them. A real image is formed by converging rays. A virtual image is one that appears to originate at the point the rays start diverging.
    Why do you think it is an image? You have a 50-50 chance just by guessing. You have to explain your reasoning.


    What is with the "Sir"? This is an equal opportunity board! Women can respond too.

  4. Jun 3, 2006 #3
    I guessed this because a pin hole camera forms an inverted image and the shadow of an upright object will never be inverted. You didn't say anything about the 3rd question. I will certainly introduce the F factor in my future queries.
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