Understanding Optics: Explaining How It Works

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Discussion Overview

The discussion revolves around the mechanics of a specific optical device involving concave parabolic mirrors, focusing on how images are formed and perceived. Participants explore concepts related to real and virtual images, the size of images in relation to the original object, and the behavior of light in this optical setup.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes the optical device and its function, noting how light reflects between the mirrors to create a real image.
  • Another participant expresses confusion regarding the terminology of "virtual image" and questions how a projection can be seen if the image is behind the mirror.
  • A participant asserts that the image is real, later correcting a previous statement about the image type.
  • There is a query about the expected size of the image, suggesting it should be half the size of the original object due to convergence at the focal length.
  • Another participant challenges the assumption that the image must be half the size, explaining that if the object is small compared to the focal length, the image can be the same size as the object.
  • A later reply indicates that the original poster resolved their confusion independently.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the image (real vs. virtual) and the expected size of the image relative to the object. The discussion does not reach a consensus on these points.

Contextual Notes

There are semantic issues regarding the definitions of real and virtual images, as well as assumptions about the size of the image based on the object's position relative to the focal point. These aspects remain unresolved.

Who May Find This Useful

Individuals interested in optics, particularly those exploring the behavior of light in reflective systems and the formation of images in optical devices.

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This is a clever toy consisting of two concave parabolic mirrors, one on top of the other, facing each other. The mirrors are made so that the focal point of one mirror is right at the surface of the other. You place a small object on the surface of the bottom mirror (inside the thing, where you can't see it directly). Since light from the object is at the focal point of the top mirror, the light reflects off the top mirror as parallel light, which then reflects off the bottom mirror to focus at its focal point: which is the the surface of the top mirror. Of course, a hole is cut out of the top mirror so that the real image can be seen. The real image looks like the object is really there.
 
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First of all, thanks for the help.

I'm still a bit confused though; it might be just some semantic problems. When you say "virtual image" do you really mean virtual image as in the image that's behind the mirror? If that were so, how we see a projection of it? Also, if the image is at the focal point, doesn't that reduce the size of the image?
 
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the image is real

Oops! I meant to say real image!
 
Still, doesn't shouldn't the image be only half the size of the orignial object if the light converges at the focal length?
 
What makes you think that the image will be half the size?

Note that light from the object isn't exactly at the focal point, since it's an object not a point source. According to my calculations, if the object is small enough (compared to the focal length) the image will be the same size as the object.
 
Never mind, I figured it out. Thanks a lot for your help.
 

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