Total Internal Reflection Demo: Water Tank

This is a demonstration of total internal reflection using a water tank.

This demonstration was created at Utah State University by Professor Boyd F. Edwards, assisted by James Coburn (demonstration specialist), David Evans (videography), and Rebecca Whitney (closed captions), with support from Jan Sojka, Physics Department Head, and Robert Wagner, Executive Vice Provost and Dean of Academic and Instructional Services.

[BackwardsHat]

Awesome. This was the perfect demonstration! Really helped me to understand the concept for my MCAT studying. Thank you!!

[nicksutton]

Thank you, this is a great demonstration. Exactly what was needed to explain to my students! I like that we can also see the laser beam refracting as it enters the water from the air.

[aarshthomas]

Awesome explanation and demo
This is everything needed to understand TIR

[sto]

Total Internal Reflection is happening right at the surface of the water... thats crazy.

[maskedmarvyl]

Question: Did you need a tank of water, or would you have the same effect if you'd used a solid thick piece of acrylic, as it would have the same boundary with the air as the water in the tank did? Was it just cheaper to use water than a very thick piece of acrylic?

[odal]

I need to say this with a caveat because I could not do this experiment and film at the same time. Having said this, I think that I get the same results with an empty water tank turned upside down. That would mean air to air refraction. Could you confirm or infirm that? Thank you.

[arnesaknussemm]

What are you adding to the water to allow the laser to be visible?

[ujveersingh]

Can you make the critical angle on all surfaces?

[lalitmohanverma]

Does total internal reflection follow laws of reflection.

[odal]

The notion of critical angle is a confession of ignorance. What makes this angle so special that light does not cross the surface like it always does? Nobody knows or even mentions the issue.