How can I have an image in space that I cannot reach out and feel with my hand?

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Discussion Overview

The discussion revolves around the optical phenomenon of seeing an image created by a setup involving parabolic mirrors. Participants explore the mechanics of how images can appear in space without being physically reachable, questioning the terminology used in optics and the nature of the images produced.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a gadget with two parabolic mirrors that creates an image of an object placed below one mirror, questioning the focal length and the nature of the mirrors.
  • A link is shared that discusses optical illusions related to similar setups.
  • Several participants express interest in a ray diagram to illustrate how the optical setup functions.
  • One participant explains that rays from the object diverge and appear to come from a point in space, leading to the perception of a "virtual object."
  • Another participant challenges the terminology, asserting that the image is a "real image" rather than a "virtual object," and later acknowledges a misunderstanding based on class notes.
  • One participant notes that the image produced by the gadget appears to hover just below the hole in the mirror, which they find frustrating.

Areas of Agreement / Disagreement

There is disagreement regarding the terminology used to describe the images produced by the optical setup, with some participants asserting it is a "real image" while others initially refer to it as a "virtual object." The discussion remains unresolved on this terminology issue.

Contextual Notes

Participants express uncertainty about the definitions of "real image" and "virtual object," and there are references to specific examples from class notes that may not fully align with the current discussion.

barryj
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There is this science gadget that consists of two parobolic mirrors, one with a hole in it and you place an item in the bottom of one, turn the other mirror with the hole on top of it, and you can see the image of the item standing above the hole in the top mirror. How is this done? Are the mirrors parobolic, I am not sure. What does the focul length have to be. I do not know of any other way that I can see an image but when I try to touch it, it is not there. Explanation Please
 
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It would be interesting to see a ray diagram showing how this works.
 
barryj said:
It would be interesting to see a ray diagram showing how this works.

The diagram they have in phinds' link shows two rays emerging from the object and converging at a point just above the device. These rays (and all the others from the rest of the object) pass right through each other and start to diverge. These rays diverge the same way that rays from a real object diverge and when you put your eye into their path the rays appear to be coming from an object hovering in air (because that's the closest point the rays are diverging from).

This imaginary object is known as a 'virtual object' in optics terminology.
 
Drakkith said:
This imaginary object is known as a 'virtual object' in optics terminology.

If by "imaginary object" you mean the image that is hovering above the device, then that is not a "virtual object." It is a "real image."
 
pixel said:
If by "imaginary object" you mean the image that is hovering above the device, then that is not a "virtual object." It is a "real image."

Whoops, you appear to be correct.
 
pixel said:
If by "imaginary object" you mean the image that is hovering above the device, then that is not a "virtual object." It is a "real image."
Okay, upon reviewing my class notes I figured out why I was confused. The example in my notes has a marginal and a chief ray intersecting and then being intercepted by a lens before they could form an image, thus forming a virtual object on the right side of the lens. I thought it was two chief rays or two marginal rays or something.
 
Off course the annoying part of these gadgets is that the object always hovers just below the hole, not above it.
 

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