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Real/Virtual Images

  1. Aug 25, 2009 #1
    What is the exact definition of a real/virtual image?

    This is what gave rise to the doubt. Suppose we have a pair of plane mirrors inclined at any angle. A point object lies on the angle bisector of the two mirrors. Now,the object sends out 2 rays,one towards each mirror. These will intersect at a point on the angle bisector after reflection from the mirrors. Is this a real image?

    If we follow this, we will find that the whole space is filled with such "images" of the object. But I feel something's wrong here.

    If we say that all rays emitted by one point of an object should meet at a single point for the image to be real, do we also imply that the image should have an intensity comparable to the object?
  2. jcsd
  3. Aug 25, 2009 #2

    Doc Al

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    Staff: Mentor

    To have a real image, light must actually converge at the location of the image. When you look at your image in a plane mirror, you are looking at a virtual image. Your image is behind the mirror, where no light actually exists.

    That's not any kind of image.

    To locate the images, imagine that the object sends out rays in all directions (many rays, not just one!). Then find where those reflected rays converge. If the rays actually do converge where the light is (for example, you can project the image onto a piece of paper) you have a real image; if they can be traced back to a point inside the mirror from which they appear to have converged from, you have a virtual image.

    Right. That would make no sense.

    No. "Rays" are just a way to visualize what's happening. There's no implication that the light will be reflected by the mirror 100%. (It can be pretty close though.)
  4. Aug 28, 2009 #3
    that makes sense. thanks!!
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