Explaining the Optical Illusion on a Spoon

  • Context: High School 
  • Thread starter Thread starter wasia
  • Start date Start date
  • Tags Tags
    Optical
Click For Summary

Discussion Overview

The discussion revolves around explaining the optical phenomenon observed when looking at one's face in a spoon, specifically why the image appears upside down on one side and upright on the other. The scope includes concepts from geometrical optics and the nature of concave and convex mirrors.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the concave side of the spoon acts as a concave mirror, producing an inverted image when the object is beyond the focal point, while the convex side produces an upright, smaller image.
  • Another participant proposes that a simple ray diagram could help clarify the explanation for both cases.
  • A different viewpoint expresses frustration that both previous answers rely on geometrical optics, implying a desire for a simpler explanation.
  • One participant argues that a straightforward explanation about the concave nature of the spoon flipping the image could suffice for a non-physics student.
  • A later reply confirms that the explanation provided is correct, but does not elaborate further.

Areas of Agreement / Disagreement

Participants express differing opinions on the depth of explanation required for the non-physics student, with some advocating for a more technical approach while others prefer a simpler explanation. No consensus is reached on the best method of explanation.

Contextual Notes

Some limitations include the potential difficulty in visualizing the concepts without drawings, and the varying levels of understanding that the non-physics student may have regarding optical principles.

wasia
Messages
50
Reaction score
0
Hello!

I have a problem - a non-physics student has asked: "Why do I see my face upside down on one side of a spoon, while it is O.K. on the other side?"

How to explain it? The only method I thought of was geometrical optics. Is it possible to clarify this phenomenon without drawing?

Thanks a lot!
 
Science news on Phys.org
One side of the spoon acts as a concave mirror (the side you scoop up with), the other acts as a convex mirror. In a concave mirror, if the object lies is at a distance greater than F from the mirror, where F is the focal dist, then the image formed is real and inverted. In a convex mirror, the image is always virtual and upright and smaller. The spoon has a very small F and that’s why you see an inverted image on the concave side, and an upright smaller image on the convex side.

If you take your face very close to the concave side of the spoon, than you will see an upright and magnified image. That’s how shaving mirrors work. In a spoon it may be difficult to see.
 
You could try drawing a simple ray diagram for both cases to aid the explanation.
 
Both answers include geometrical optics :(
 
Well so what? I think a person able to ask that question could understand a simple, ''the concave nature of the spoon acts as a mirror which flips an image at its focal point''. How deep of an answer is your friend looking for?
 
That is the correct answer!
 

Similar threads

Replies
12
Views
2K
  • · Replies 37 ·
2
Replies
37
Views
5K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 49 ·
2
Replies
49
Views
13K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K