Total Internal Reflection a doubt?

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SUMMARY

The discussion centers on the concept of total internal reflection (TIR) in mirrors, clarifying that the scenario described involves partial internal reflections rather than total internal reflections. The participants explain that light rays undergo a sequence of reflections and refractions, with the critical angle determining the behavior of light at the mirror's surface. The confusion arises from the terminology used, as the process described includes both partial reflections and refractions, leading to light emerging from the mirror. The real-world application of this principle is likened to the functioning of fiber optic cables.

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  • Understanding of light behavior, including reflection and refraction
  • Familiarity with the concept of critical angle in optics
  • Knowledge of total internal reflection versus partial internal reflection
  • Basic principles of how mirrors and fiber optics operate
NEXT STEPS
  • Study the principles of total internal reflection in detail
  • Explore the critical angle and its implications in optical systems
  • Investigate the design and functioning of fiber optic cables
  • Learn about the differences between partial and total internal reflections
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Students and professionals in physics, optical engineering, and anyone interested in understanding the principles of light behavior in reflective surfaces and fiber optics.

archijun3
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I was reading about a case of total internal reflection in mirrors and something got me curious...
Is there anything such as 'weak refractions'??
In the diagram of the mirror I saw, as a ray of light from an object entered a mirror, it was reflected by the silver coating, and then by the surface of the mirror (assuming it's because of total internal reflection). This process was repeated three times more, and the light ray emerged out of the mirror.
The doubt I have here is, everytime the ray of light was reflected off from the surface of the mirror (total internal reflection), there was a ray of light exiting the mirror at that point. Where exactly did that ray of light come from?

Plus, if I may ask further, how many times will total internal reflection have taken place in the above situation?
 
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I believe the example you are looking at is demonstrating "partial internal reflections" not "total internal reflections".

See the diagram below (from.. http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/totint.html).

On the left the angle of incidence is such that the light is partly relected and partly refracted.

As the angle changes there is a point at which the light that emerges is refracted along the surface. This is called the critical angle.

On the right the angle is such that the light is totally reflected and no light emerges.

totint2.gif
 
Last edited:
archijun3 said:
Plus, if I may ask further, how many times will total internal reflection have taken place in the above situation?

I make the sequence..

A refraction
A reflection off the silvered surface
A partial internal reflection (some light emerges)

This is then repeated three more times..

A reflection off the silvered surface
A partial internal reflection (some light emerges)
A reflection off the silvered surface
A partial internal reflection (some light emerges)
A reflection off the silvered surface
A partial internal reflection (some light emerges)

Because the very last reflection is partial there will be a faint emerging ray which is the one you describe as leaving the mirror.

In the real world you would probably get a lot more internal reflections because mirrors have parallel surfaces. That means once the ray is bouncing around between the surfaces the angle of incidence doesn't change much so there is nothing but the edge of the mirror to stop internal reflections. That's more or less how crude fiber optic cables work.
 
My thanks to CWatters :)
So this is an example of partial internal reflection isn't it??
I was confused because the heading was written as total internal reflection..zz
It's been a great help xD Thank you!
 

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