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Please help I need to prove a physics teacher wrong

  1. Sep 20, 2011 #1
    1. The problem statement, all variables and given/known data

    I'm not able to understand this misconception
    "An observer can see more of their image by moving further back from the mirror"

    2. Relevant equations

    3. The attempt at a solution
    I tested and I believe I can see more of the image as I move further back from the mirror, but I know it needs to be something with visuals, or with the angle that the object reflects but yet I'm not able to come up with a conclusion. Please help I'm a biology major and have never taken any physics courses.
  2. jcsd
  3. Sep 20, 2011 #2


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    Homework Helper

    You can test this practically, or derive it theoretically, but either way the statement is incorrect, and indeed a common misconception.

    As you move closer to a mirror, you can see more and more of the surroundings [the image of the surroundings reflected in the mirror] - but as you get closer, the image of yourself also gets bigger, so you don't see a greater expanse of that. By getting bigger I am referring to the "Sesame Street" idea/song , that things look bigger when they are closer up.
  4. Sep 22, 2011 #3


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    Gold Member

    This is one of those statements that is suposed to make you think about angle of incidence and angle of reflection, both of which in a mirror are equal. As you move farther from the mirror both angles decrease. If at the bottom of the mirror you can see your belly button, than farther away you will again see no farther down than your belly button. And that is why it is a misconception, and what them mean from a textbook point if view.

    But that is only for people or objects that are flat.
    As we know people are not flat, but have curves and protusions.
    Look at your face in the mirror from say 3 feet away. Then move closer. as you move closer, you will notice that parts of your face begin to disappear from view. You cheeks may begin to hide your ears and sides of the face. Your chin may hide you neck, and since the top of your head is curved you will see less and less of that part.

    So is the statement a misconception or not. It depends on the point of reference.
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