The simple mathematics you can use to motivate one of the best and easiest physics demonstrations ever

The Disappearing Beaker

Hope ConcannonThe North Carolina School of Science and Mathematics1219 Broad StreetDurham, NC 27705email: concannon@ncssm.edu

We have all experienced

refraction when we

notice the apparent

bending of an object

when it is dipped in

water. What is really

going on here?

http://eyestravel.eu/wp-content/uploads/2013/03/refraction.jpg

http://www.opticampus.com/nature_light/images/Slide13.GIF

http://www.patana.ac.th/secondary/science/anrophysics/ntopic4/images/car_refraction.jpg

The Law of Refraction

Notice the tie between this equation and the Law of Sines!

Light bends at a boundary between two

materials with different optical densities.

Some implications and activities using the Law of Refraction

http://www.gareyscience.com/ana22/waves_online_lesson/refraction-pencil-all.jpg

If you want a quick lab,

students can measure the

angle of incidence and

angle of refraction and

verify that the Law of

Refraction describes what

they see.

http://farm5.static.flickr.com/4129/5079318821_8ac68e77f5.jpg

Think about the direction light

bends when traveling from

water into air. What happens

when the exiting ray travels

along the surface of the water?

What happens at even steeper

incident angles?

Total Internal Reflection

http://theboard.byu.edu/media/attached_files/r_96768/Total-Internal-Reflection.gif

Is there an incident angle where the light will

exit along the boundary surface (

becomes

This has a solution only if light is speeding up

at the boundary (so and )!

Optical Fibers

https://webspace.utexas.edu/cokerwr/www/index.html/tubeinoil.JPG

http://gr5.org/index_of_refraction/babywess.jpg

Where did the pipette and test tube go?

A full handout of this talk will be available on

the web after this conference at

http://courses.ncssm.edu/talks/conferences/

Thank you for coming!