Understanding Light Refraction: Why a Ping Pong Ball Looks Bigger in Water

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Discussion Overview

The discussion revolves around the phenomenon of light refraction as it pertains to the visual perception of a ping pong ball submerged in water. Participants explore the reasons behind the apparent magnification of the ball when viewed through a thick glass container filled with water, touching on concepts of optics and the behavior of light in different media.

Discussion Character

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

Main Points Raised

  • One participant notes that the cylindrical shape of the glass and water acts as a lens, causing magnification due to light refraction.
  • Another participant suggests that the non-flat surface of the water bends light into a new path, spreading it outwards.
  • A question is raised about the nature of the water surface and its impact on light bending, seeking clarification on the term "bent outwards."
  • Discussion includes the principle that light changes velocity when moving between media of different densities, which contributes to magnification.
  • Participants consider whether the combination of water and the cylindrical glass creates a cylindrical lens effect, with some noting that magnification occurs along the horizontal axis but not the vertical.
  • One participant mentions the sufficiency of the ray approximation of light for understanding the image, while also suggesting that wave optics and classical electrodynamics could provide deeper insights.

Areas of Agreement / Disagreement

Participants express various viewpoints on the mechanisms of light refraction and magnification, with no clear consensus reached on all aspects of the discussion. Some participants agree on the lens-like behavior of the glass and water, while others seek further clarification and explore different angles of the phenomenon.

Contextual Notes

There are unresolved questions regarding the specifics of light behavior at the water surface and the implications of using different optical models (ray vs. wave optics). The discussion also highlights the complexity of understanding the interaction between light and different media.

Who May Find This Useful

This discussion may be of interest to individuals studying optics, physics, or anyone curious about the principles of light refraction and visual perception in different mediums.

md6616
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i need an explanation for this situation.
i've inserted an pingpong ball into a glass full with water (the glass is made out of thick glass if it matters somehow?).
Now what happened is that the half of the ball that is in the water looks much bigger than the half that is not in the water.

My question is why the ball that is in the water looks so big? how does it connected to light refraction?

p.s- I added a sketch for you to understand better the situation!

:smile:

A reply would be very much appreciated
 

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The cylindrical shape of the glass+water acts as a lens, magnifying the ball. Lenses cause this magnification because of the way light refracts.

Claude.
 
!

Many thanks for your fast reply :)
Would you mind adding a more detailed explanation or to direct me to website that will explain it more clearer?
 
Since the water surface is not flat - because of the container and other factors. The light is bent into a new path. The light is bent outwards and is spread out.

http://en.wikipedia.org/wiki/Refraction
 
ranger said:
Since the water surface is not flat - because of the container and other factors. The light is bent into a new path. The light is bent outwards and is spread out.

QUOTE]

Thanks for your reply :)
I'm not so sure i understood your answer!
Why does the water surface isn't flat?
and what do you mean by "The light is bent outwards"? outwards from where?
and how it causes the ball to look magnified? ( is it because the combination of water and glass acts like a magnifying lens like Claude said?)
 
md6616 said:
ranger said:
Since the water surface is not flat - because of the container and other factors. The light is bent into a new path. The light is bent outwards and is spread out.

QUOTE]

Thanks for your reply :)
I'm not so sure i understood your answer!
Why does the water surface isn't flat?
and what do you mean by "The light is bent outwards"? outwards from where?
and how it causes the ball to look magnified? ( is it because the combination of water and glass acts like a magnifying lens like Claude said?)

In order to understand how an immersed object is magnified, I guess an understanding on how a typical magnifying glass magnifies an object would be a good start. They make use of the principle that light changes velocity as it travels in mediums of different densities. As light moves from air to a more dense medium, let's say water, the light in refracted (bent) [towards the normal]. The larger the change in the index of refraction, the more the magnification.

Now imagine that you and the ball are both immersed in water. Do you think there would be magnification? Why [or why now]? To complicate the situation, what if you had a magnifying glass with you under water?

So what you said is correct - it does act like a kind of lens.
 
Thanks ranger :)
 
one more question!
Does the combination of water and cylinder shaped glass creats the effect of cylindrical lens?
 
Anyone want to attempt a QED explanation?
 
  • #10
md6616 said:
one more question!
Does the combination of water and cylinder shaped glass creats the effect of cylindrical lens?

Yes, you'll notice that the ball is magnified along the horizontal axis but not the vertical.

Claude.
 
  • #11
3trQN said:
Anyone want to attempt a QED explanation?
:smile: lol. why?
 
  • #12
illustration
 

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  • #13
cesiumfrog said:
:smile: lol. why?

I was just curious :rolleyes:
 
  • #14
hmm...if light rays are basically refracted further apart, then why don't we get a certain distortion (blind spots)?
 
  • #15
3trQN said:
just curious

In this domain, the ray approximation of light is sufficient to understand the image (combined with snell's law of refraction).

If you wanted, you could try to understand snell's law of refraction. You could do so by switching to wave (rather than ray) optics (combined with knowledge of the wave velocity in various media).

If you wanted to understand why wave optics is relevant (and why the wave velocities differ among media), you might study classical electrodynamics. In depth. I'm just saying it would be a long time before you understood the physics of your problem well enough to be able (or to need) to use quantum electrodynamics to further improve your understanding.
 
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