Density+and+Optics

We might sometimes forget about the density of objects in our everyday life, but light waves never do. You see, the speed light can travel depends on the density of the material, or "medium," that it is traveling through. Imagine walking through a crowded hallway packed with people. This would take you a longer time to move through than an empty hallway. For light it is the same way, in mediums where the particles are more densely packed that light travels slower. The speed of light we all are familiar with, 3x10^8 m/s, is based on light traveling in a vacuum of space- with a density 0! The way light slows down in every other medium causes it to bend- which can lead to some crazy optical effects we have all noticed! This bending is called refraction. At the taggalaxy.de site, you can search millions of photos from flickr to find examples of these effects. In the screen shot below, the term refraction (when light bends due to a change in speed) was searched. Why do you think there are so many shots of water droplets? Other terms you might want to try are: Snell's law and optical effects. taggalaxy site
 * Density & Optics**

Here is a great explanation of refraction and Snell's Law: refraction, Snell's Law and diagrams

Here is a website to practice your understanding to Snell's Law and refraction: Snell's Law Applet

Teacher's Corner: The following pdf is for a lab using jello and laser pointers to calculate the index of refraction for jello. Some notes on the supplies: Unflavored gelatin works the best for this lab, although any jello prepared as a jiggler will work. Lighter jellos, like yellow and green are easier to use than darker reds, especially if your laser pointers are red! Pour the jello into rectangular tupperware to get it to school safely. Run warm water under it to pop them out without ripping the edges.

Wolfram Alpha has a lot of great Snell's Law calculators. The following widget will allow you to see all the resources on their site for Snell's Law. Using this widget from Wolfram, you can calculate the angle of refraction, angle of incidence, & index of refraction for both mediums : media type="custom" key="9757962"

Here is a video that captures the magnificence behind the man who was Snell: media type="youtube" key="dWwQqI2BkVc" height="349" width="425"