fingerprints on glass

Numeriprimi

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.

Drakkith

Frustrated Total Internal Reflection.

http://en.wikipedia.org/wiki/Total_i...nal_reflection

I'm a bit tired and it's time for bed, otherwise I'd elaborate more. Browse through the links on the article if you find you don't understand something, and feel free to ask more.

Numeriprimi

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?

CWatters

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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Drakkith Recognitions: Gold Member	Frustrated Total Internal Reflection. http://en.wikipedia.org/wiki/Total_i...nal_reflection I'm a bit tired and it's time for bed, otherwise I'd elaborate more. Browse through the links on the article if you find you don't understand something, and feel free to ask more.

Numeriprimi	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?