Problem with light grazing along the liquid surface

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Discussion Overview

The discussion revolves around the behavior of light grazing along the surface of a liquid in a cuboidal tank, particularly focusing on the visualization of light paths and the implications of the critical angle. Participants explore the effects of light from various parts of the tank entering the observer's eyes and the application of the reversibility principle of light in this context.

Discussion Character

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

Main Points Raised

  • One participant questions what an observer would see when light rays from different parts of the tank strike their eyes, suggesting confusion about perceiving multiple parts of the tank simultaneously.
  • Another participant proposes that the observer would not see a distinct image of the tank's bottom but rather a summation of light from various parts, visualizing it as a squashed image.
  • A participant raises a concern regarding the application of the reversibility principle of light, questioning how light rays grazing along the surface would also imply that light from the observer's eye should enter the liquid at the critical angle, finding this notion strange.
  • One participant introduces the idea of light scattering and challenges the neatness of ray optics, suggesting that the reality of the water-air boundary involves complexities that ray optics may not adequately describe.

Areas of Agreement / Disagreement

Participants express differing views on the visualization of light paths and the implications of the reversibility principle. The discussion remains unresolved, with no consensus on the interpretation of these phenomena.

Contextual Notes

Participants acknowledge limitations in the ray optics model and the complexities of light behavior at the water-air boundary, indicating that further exploration beyond ray optics may be necessary.

GAURAV DADWAL
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Let's suppose we have a cuboidal tank filled with liquid of density rho,such that
Critical angle of medium is (Ic) now it's
Clear that light rays from the medium that strike at proper critical angle will
Graze along the surface
Now if someone would be along the path of the rays receiving them into his eyes I'm not able to visualize what he will see as light from many parts will be coming into his eyes at once .does that means he will be seeing many parts of tank together at same place this is confusing .please let me have deeper insight into situation Thanx to all those who will help
 
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You have it right, I think. You won't see an image of the bottom of the tank, just the sum of all the light coming from the bottom (and sides) of the tank. You could imagine it as an image squashed down to zero height.

You could try it. Get a shallow box or a dish with a pattern on the bottom. Fill it to the brim (can you get an inverted meniscus?) with water. Put it near the edge of a table, let it settle, and then look at it from above. Then just kneel down until you're looking along the surface. As you do, you'll see the pattern on the bottom squish down to nothing.

Compare what you see when the dish is empty.
 
Also i had a problem on applying reversibility principle of light in this case
Like how light rays from different parts of tank are grazing along surface ,the principle of reversibility predicts that light from eye that grazes along surface should also enter the medium of liquid at all points at an angle equal to critical angle of medium
But this seems weird pls correct me if I'm wrong somewhere
 
Why is the sky blue? Because light both passes through it and scatters off it. That's really only a plausibility argument for the idea of light scattering in multiple places along the surface, butvthe idea isn't totally absurd.

In fact, ray optics is an idealisation. If you think about what the water-air boundary really is - a collection of molecules jiggling and bouncing around - do you really think light will travel neatly along the continually shifting surface? You're going to have to go far beyond ray optics to get a completely satisfactory description of it.
 

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