The

Demonstrations

To  help the students understand the slowing of light as it changes medium, the analogy of runnin on different surfraces was used. It is impossible to run through water at the same speed as on land.  This was then expanded to include an army crossing a river at an angle. The soldiers entering the river first will slow down and lag behind those who have yet to enter the river. This causes the direction the formation is travelling in to change as they enter and exit the river. The students then demonstrated this themselves walking in rows of 5 down the hallway. Two strips of tape were laid down as an imaginary "river" for the students to walk through. 

A simple pencil in water trick was also used in conjunction with an illustrated diagram (featured on the Home Page) to show the students exactly what happens optically when light exits one medium and enters another. The apparent location of the portion of the submerged pencil appears to be where we percieve the light rays to originate from, this is why we see a pencil either bend or break when placed in water depending on the angle at which we look at it.

Refraction based on wavelength/energy of light was introduced to the students using a prism, then demonstated by passing two different colors of laser pointer through a jar of water. The two colors used (red and green) refracted at different angles. This is a physical result of Snell's Law which dictates that the angle of refraction not only depends on the index of refraction of the medium light travels through, but also its wavelength. To help the students understand why higher energy/shorter wavelength of light refract more, the analogy of running in water was used again. The slower you walk into water, the farther you can go. If you run into water, you will not be able to maintain that same speed very long. Shorter wavelengths lose more energy as they change medium and therefore refract more.

A final demonstration was made to help the students visualize the consequences of indices of refraction. Two Pyrex test tubes were submerged into a glass full of vegetable oil. One of the tubes was then filled with the same oil and "disappeared".  Vegetable oil and Pyrex have very similar indices of refraction, which means that the two are essentially obtically indiscernible.