Activity 2


 
The Bent Pencil


Introduction

Dangling your legs in the calm pool on a hot summer day, you notice that your legs look broken right under the surface of the water. Your legs seem to take a 30° turn where they go into the water! You sure didn't feel any pain when you put them in....Taking them out, they look fine, back to normal. Why is this?

Procedure

  • Gather these items from your home or workplace:
    • a glass of water
    • a pencil

  • Looking from above the glass, place the pencil into the water and notice any changes to its appearance.

  • Also look at the pencil from the side of the glass and up towards the water surface.

  • How can you explain this phenomenon? Of course, you're saying to yourself, it's just light bending in the water. But is light really bending as it goes through the water? Where exactly does the light bend?

  • Plus, which way is the light bending if you see the pencil with a kink in it? Draw yourself a diagram showing the pencil and how light from the pencil gets to your eyes.

  • You can also try out the Java applet below that lets you manipulate a light beam entering different materials.

Demonstration of Snell's Law

Use the slider on the left side to change the angle of incidence of the light beam.
Use the buttons on the right side to change the materials in which the light beam travels.


Go to the Refraction Readings when you're done with this Activity.



Page authored by ACEPT W3 Group
Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504
Copyright © 1995-2000 Arizona Board of Regents. All rights reserved.
Java applet by Douglas Beeson (with refinements and errors by Steve Beeson -- just emulating big bro)