# How much of himself a person can see in the mirror? [closed]

A man who is $6$ ft tall is standing in front of a plane mirror that is $2$ ft in length. The mirror is placed lengthwise with its bottom edge $4$ ft above the floor on a wall that is $5$ ft away(Assume that his eyes are right at the top of his head).
1) How much of his image (i.e. what length of himself) can the man see?
2) How much of the $8$ ft-tall tree behind him, $10$ ft away from the wall, can he see?
3) When the man moves to stand next to the tree, with the mirror staying in place, how much of himself can he now see? How much of the tree can he now see?

Attempt:1) I know about the $2:1$ rule so since the mirror is $2$ ft long he must be able to see the upper four ft of his body. Does the distance from the mirror matter though?
2) He should not be able to see the tree because he himself is covering it. I am not sure about that. Hints please.
3)The answers will be the same as in two previous questions. Again I am really not sure about that. An intuitive explanation or hint would be great. Thanks.

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## closed as off topic by dmckee♦Jun 1 '12 at 3:51

Questions on Physics Stack Exchange are expected to relate to physics within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.

Welcome to Physics.SE, Dostre. I'm glad to see that you have received some good advice below, but our FAQ is quite clear that this is not a homework answer service. You are welcome to ask questions about basic concepts (such as those in ray optics), but not to ask us to solve particular problems. – dmckee Jun 1 '12 at 3:53
I did not ask to solve a problem. I asked whether my reasoning was correct. And it is a basic physics concepts. The problem is just a mere example. And you have that tag, so you are a little picky, no disrespect. – Koba Jun 1 '12 at 4:04
Re:[closed]. But but. What if it was a physicist who built a transporter into parallel universe. And getting this answer is the only way to detect what symmetry laws permutation is valid here. – user299 Jun 1 '12 at 4:12
"I asked whether my reasoning was correct." You have still asked for a solution to a basic exercise. @RocketSurgeon: A physicist would be able to deduce the answer for herself, and by chance she could not she could ask about the concepts of ray-optics or forsake the Stack Exchange network and find another physicist to ask in person or by email or or or – dmckee Jun 1 '12 at 4:16

Well, 2:1 rule is not as good as looking directry to rays. Trace the rays and ... well you'll see. Comparing triangles is one, not the only one, approach to geometric figure.

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can you elaborate on that? – Koba Jun 1 '12 at 3:38
will be good idea to name points on head, mirror, tree and so on, get the triangles, with imaging method (other answer) or directly $\alpha=\beta$ law; also, you have transparent batman, or add one more dimension – sanaris Jun 1 '12 at 3:55

The line from eye to top of mirror on your picture can be continued to far right. Draw same line from eye to bottom of mirror and continue beyond the mirror. Add second dude to the right side of the mirror facing the opposite way.

See if top and bottom line intersect or overshoot the second dude. The portion of dude in between lines is an answer.

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ok makes sense. What about parts 2 & 3? I think they are correct. – Koba Jun 1 '12 at 3:51
For the tree: draw a mirrored tree to far right, same distance. Extend lines straight more and check what falls between the lines. For new view point repeat lines drawing after moving both dudes. – user299 Jun 1 '12 at 3:55