Total Internal Reflection

[sciart]

Do you think total internal reflection is a kind of refraction?why?

[timo]

What do you think? And why?

[sciart]

I am not sure .

[Klaynos]

Consider what is happening and what refraction is, and then compare the two...

[mattbimbo]

yes, the phenomenon of TIR causes 100% reflection of the incident wave. well maybe not 100%, but close to, because there is a phenomena involving TIR and the propagation of an evanescent wave.

[swansont]

yes, the phenomenon of TIR causes 100% reflection of the incident wave. well maybe not 100%, but close to, because there is a phenomena involving TIR and the propagation of an evanescent wave.

 

Why do you consider that refraction? Reflection still happens at angles where refraction can occur.

[mattbimbo]

TIR occurs at the interface of two media. the angle of TIR is determined by the relative refractive indices of the two media.

[swansont]

TIR occurs at the interface of two media. the angle of TIR is determined[/b'] by the relative refractive indices of the two media.

 

Reflection occurs at the interface of two media as well. The angle of the reflection is not determined by the indices; the angle where refraction fails to occur is.

[mattbimbo]

swansont is right. TIR always appears in text books under refraction.

 

maybe swansont will approve of this - when light is incident on a surface both reflection and refraction take place, however in the case of TIR, no refraction is observed, hence the name TIR.

[swansont]

swansont is right. TIR always appears in text books under refraction.

 

maybe swansont will approve of this - when light is incident on a surface both reflection and refraction take place' date=' however in the case of TIR, no refraction is observed, hence the name [b']TIR[/b].

 

Not that my approval is necessary, but that's the direction my argument was going, so I agree. TIR occurs because of the absence of refraction.

 

BTW, there are some neat underwater shots I've seen that show this. The area you can see outside the water is "Snell's window" (or circle) and outside of that everything is undergoing TIR, unless there is some disturbance in the water, in which case the direction of the normal changes.

[s pepperchin]

Do you have a link where we could see this picture?

[swansont]

I haven't been able to find the one I'm thinking of (a diving swimmer just entering the pool) online, but here is a pretty good one, and another that shows part of Snell's circle.

[swansont]

Found some more TIR swimming pics by Heinz Kluetmeier

 

http://pdngallery.com/legends/heinz/intro2.html

http://pdngallery.com/legends/heinz/main06.html

http://sportsillustrated.cnn.com/multimedia/photo_gallery/0608/gallery.swimming/content.4.html

http://sportsillustrated.cnn.com/multimedia/photo_gallery/0608/gallery.swimming/content.8.html