Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Settle my dispute- Can you see more of yourself in a mirror?

  1. Mar 25, 2007 #1
    When standing in front of my bathroom mirror (on the medicine cabinet above sink), I start to walk backwards.

    Will I be able to see more (or less) of my body in the mirror as I walk away from the mirror? Why? (For example, if I cannot see below me knees or above my eyebrows, will that change as walk away from mirror)

    As you may guess, I know very little about physics. If possible, please explain your answer as simply as possible.

    The mirror is flat against the wall.

    Thank you in advance for your feedback.
     
  2. jcsd
  3. Mar 25, 2007 #2
    More, because the counter's not in the way? I'm not entirely sure, really.
     
  4. Mar 25, 2007 #3
  5. Mar 25, 2007 #4
    its all geometry. if someone is standing on the other side of a small window, you can see more of them the farther away they stand from it. the same principle with a mirror, except you are seeing yourself
     
  6. Mar 26, 2007 #5

    AlephZero

    User Avatar
    Science Advisor
    Homework Helper

    There is a problem with that logic. If you want to get your reflection to "move" further away from the mirror, then YOU have to move further away as well.

    The way to answer the question is to do an experiment. Stand close to the mirror and draw the outline of your face on the mirror surface (use something that you can clean off easily, of course!!!). Then stand further back and "fit" your reflection on top of the drawing. It's easy to see if it stays the same size or not.
     
  7. Mar 26, 2007 #6
    Imagine a very large diameter cylindrical mirror near whose axis of symmetry you are standing. If you are vanishingly small in comparison to the mirror, you will not block your image which is being reflected back to you in 3600. The possible shapes of 3600 mirrors you can utilize approaches infinity. You can test the hypothesis in three dimensions, where you are near the center of a silvered sphere, or mirror likewise covering 4pi steradians.
     
  8. Mar 26, 2007 #7

    marcusl

    User Avatar
    Science Advisor
    Gold Member

    Can anyone explain what this means? I don't get it :uhh:
     
  9. Mar 26, 2007 #8
    I dont get it either. just nod and say you agree :shy:
     
  10. Mar 27, 2007 #9
    Basically, if an arbitrary mirrored surface is normal to you through much of your perspective, if you are small relative to the distance from the mirror and you are not at the focus of the mirror, you may see considerably more of yourself than in a plane mirror. With two plane perpendicular mirrors separated from a corner (as in many bathrooms), there tends to be a blind spot, no matter how one adjusts her viewpoint.

    Some cosmologists theorize that many galaxies we see in deep space are multiple images (some even backwards?) arising from the curvature of the universe bending light.
     
  11. Mar 27, 2007 #10
    It's just a simple geometric problem. What you see yourself in a mirror is always double the size of the mirror regardless how far you stand from the mirror.
     

    Attached Files:

  12. Apr 1, 2007 #11
    I disagree with all those answers. I think the key to this problem is to consider this following experiment. Imagine you are in your backyard, lying down on your front facing the ground. You are so close to the Earth that you can only see the grass in front of you. Now imagine you are likewise facing the Earth, but you were suspended 80 miles up in the air by a giant crane hoist attached to your belt buckle. Now you would start to see part of the curve of the Earth and thus more of it. In fact, the further you get from the Earth, the more of it you can see.

    The same goes for the mirror. When you stand nose pressed to the mirror you see very little of you face. When you back off 1 foot you can see most of your face including your ears When you back stand back a few feet you can see even more of your face.

    This happens because you have a fixed field of view that can see almost everything, in front of your shoulders, but not quite. If you could have a field of view that saw everything perfectly in front of your soldiers, you could stand a foot in front of a store on a main street and see every other store on the same side of this street.
     
  13. Apr 1, 2007 #12
    Hi Chaos, may I ask you a small question.
    Have you ever tried with a mirror mounted on the wall vertically in your home?. I think you should do that first.
     
  14. Apr 1, 2007 #13
    Why, explain.
     
  15. Apr 1, 2007 #14
    If the mirror is vertical, you stand vertically, so how much you can see yourself in the mirror is unchanged regardless you step forward or backward. And that answers the question of this thread creator.
     
  16. Apr 1, 2007 #15
    Interesting question that I haven't heard before---


    I personally would think that you may see less of yourself:

    Refraction (through the glass) should make the image (your image of yourself--let's say chin and top of head back to the eyes) 'appear' closer.
     
  17. Apr 1, 2007 #16

    Janus

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    As long as your image in the mirror fits in your field of vision, You will see the same amount of yourself in the mirror. It is only when you get close enough to the mirror that your image goes beyond your field of vision do you see less of yourself.
     
  18. Apr 1, 2007 #17

    Wouldn't the size of 'your' image only be the 'same' only if the angle of incidence and the angle of reflection was 'zero' through the glass (no refraction)?
     
  19. Apr 1, 2007 #18
    A planar mirror has no net refraction since the light passes through the glass, bounces off the silvered backing and then back through the glass, thus canceling out the refractions.
     
  20. Apr 1, 2007 #19
    All light will have an incident angle EXCEPT the light reflecting back and forth to the open eyes.

    The way it appears to me (as I think about it) is that the deviated path of the light ray will reflect off of the mirrored surface (after going through the glass) and reflect at that higher incident angle. It will refract on its outward path too, but will 'emerge' from the glass closer to the point of it's entrance into the glass.

    If it wasn't refracted (the undeviated path) reflection path would exit the mirror at a greater distance from its point of entry into the mirror than the exit point of the deviated/refracted path. The refracted and reflected ray would have to have a closer point of initial light source (on the face) and would make the face smaller to be reflected into the eyes. The items of the face that are farther from the eyes would have a greater difference (in the difference between entrance/exit) due to the greater refraction, too. If you're infinity far from the mirror :rolleyes: , I don't think that there would be any distortion from the 'real' size and the 'reflected' size.

    http://www.antonine-education.co.uk/Physics_AS/Module_1/Topic_2/Refract_1.gif


    This image shows glass with no mirror, but if the mirroring surface was on the bottom, it seems that it would show what I think.


    ----------------------------------------------------------------


    The answer (above) as I read the initial post is for the 'title' of the post.

    The answer to this question is 'perspective'. The farther you are away (you get) from an object the smaller it becomes. This would be true of the virtual image too (mirror/reflected image); that is, as you move backwards, you see 'more' (if the mirror is small and you only see part of yourself at first)--just as if you were standing nose to nose with someone and starting walking backwards--you would see 'more' of the person in front of you as your field of vision increased of that person.


    http://en.wikipedia.org/wiki/Perspective_(visual)



    The reason I gave at the beginning of this I think got a little deeper than the OP question posed.
     
    Last edited: Apr 2, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Settle my dispute- Can you see more of yourself in a mirror?
Loading...