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Homework Help: A mirror reflection of a mirror reflection

  1. Nov 14, 2013 #1
    a mirror reflection

    1. The problem statement, all variables and given/known data


    Create a set-up, as shown in the Figure, consisting of two mirror tiles (A and B)
    and a bird face, facing to the right . Make sure the two mirrors are perpendicular to the table and parallel to each other. The situation shown is a front view of the situation.

    A: If look at a mirror from the same direction and angle as one of the two arrows that are drawn, you will see the bird in the mirror. Draw the two mirror images of the bird, making sure the bird mirror is facing to the correct side!

    B: Also add mirror image B' of mirror B to mirror A.

    2. Relevant equations
    mirror images

    3. The attempt at a solution

    I tried to draw a mirror reflection.
    But Can the light ray (in yellow) simply go through the bird?
    Last edited: Nov 14, 2013
  2. jcsd
  3. Nov 14, 2013 #2
    Hey there!

    Use the laws of reflection which states that :
    a.The angle of incidence is equal to the angle of reflection.
    b. The incident ray, reflected ray and the normal to the surface lies in the same plane.

    Now, It is to be kept in mind while tracing the image on an object that, no image is formed if there is no reflection.
  4. Nov 14, 2013 #3
    I know this, but A is a mirror! Of course there is reflection on a mirror! Have you actually read the question??? And you suppose to see the bird in mirror A, as stated in the question.
  5. Nov 14, 2013 #4


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    You could certainly argue that from position B you will not see the whole image. In particular, you will not see the near side of the bird (the far side of the image). Whether a light ray on the line shown will reach you is not clear, since we do not have a plan view of the set-up. It could be that B is much closer to us than is the bird.
  6. Nov 14, 2013 #5
    The yellow line drawn does not follow the direction of the arrow B. It is at an angle to it.

    If I read the question correctly it is implying you will only see an image of the bird from one of the two positions. If that is the case, remembering to apply rule a. stated helpfully by phyneach, that you are already aware of, draw STRAIGHT lines and see which position actually has a "line of sight" to the bird.

    (At a glance, perhaps it is not position B, but I could be wrong)

    Consider why the outer two lines are given in this problem. They seem very conveniently positioned for where one might expect a virtual image to appear or be drawn as an answer.

  7. Nov 14, 2013 #6
    @haruspex: "we do not have a plan view of the set-up. It could be that B is much closer to us than is the bird" <-- No, this would make it too complicated, simply expect that this is not the case, you can see the bird in the mirror if your x-position is at A or B and your Y-position is at a higher point than the mirror itself.

    @mic*: "The yellow line drawn does not follow the direction of the arrow B. It is at an angle to it." well, how would you draw the line???
  8. Nov 14, 2013 #7
    Also: how would you add "mirror image B' of mirror B to mirror A." if some parts are obscured??
  9. Nov 14, 2013 #8
    Did you click the link I attached?
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