Why Do Fingerprints Appear on Glass When It's Filled with Water?

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The discussion centers on the phenomenon of frustrated total internal reflection observed when viewing fingerprints through a cylindrical glass filled with water. Participants explore why only fingerprints are visible while other parts of the glass appear mirrored, attributing this to the interaction of light with different refractive indices. Suggestions are made regarding alternative materials that could produce similar effects, emphasizing that any medium with a higher refractive index than air can create an evanescent wave. The conversation also touches on the conservation of energy in relation to evanescent waves and how they can transmit energy under specific conditions. Overall, the thread delves into the optical principles behind this intriguing visual effect.
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My thinking today at lunch ...
You fill up the cylindrical glass with water. You take it to hands and you can see fingerprints through the water. The others parts of glass is like mirror. Why you see only fingerprints and nothing else? Can you see similar phenomenon if you use something different on glass? And why is that? What's happens after emptying the glass or fill on with different liquid and why?

Sorry for my bad English and thanks for your answers.
 
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Ok, it looks good, I will read it after school.
Is an another example of this phenomenon? (no fingers). What can I put on the glass for this phenomenon?
 
It says..

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the low-index second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

The first medium is the glass, the second is air, and the third is finger.

So you should be able to do it with any material that has a higher refractive index than the air.
 
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