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Objects in Mirror closer than appear Concave or Convex

  1. Feb 5, 2015 #1

    grandpa2390

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    1. The problem statement, all variables and given/known data
    When a T.rex pursues a jeep in the movie Jurassic Park, we see a reflected image of the T.rex via a side-view mirror, on which is printed the (then darkly humorous) warning: “Objects in mirror are closer than they appear.” Is the mirror flat, convex, or concave?

    2. Relevant equations


    3. The attempt at a solution
    The answer is convex, but i dont think that is right. One place said the reason is because it gives an upright small close image. as the image is diminished, the image distance is small when compared to the object distance. and this is the reason for the warning. To me this says the opposite. If the image distance appears smaller than what the object distance is, shouldnt the warning read: Warning: objects in mirror appear closer than they really are. lol.

    my opinion is that the mirror is concave. that way the image is small and far. and that is the point of the warning. it is telling you that i=10 when p actually equals <10. so you dont make a lane change thinking you have more space than you really have.

    is the question writer interpreting the warning wrong, or is the explanation wrong? or am i just misunderstanding.
     
  2. jcsd
  3. Feb 5, 2015 #2

    TSny

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    If the mirror is concave, would the image of a very distant object be upright or inverted? Does that correspond to experience for a side view mirror of a car?

    Yet, as you say, the image distance in a convex mirror is less than the object distance.

    When interpreting the distance of what is seen in the mirror, maybe the brain is more influenced by the size of the image than by the distance between the image and the mirror.
     
    Last edited: Feb 5, 2015
  4. Feb 7, 2015 #3

    grandpa2390

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    are you saying that a convex mirror will make the image appear smaller and a concave mirror will make the image appear larger?
     
  5. Feb 8, 2015 #4

    TSny

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    The image size is always smaller than the object size for a convex mirror. For a concave mirror, the image can be bigger, smaller, or the same size as the object.
     
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