Phet Bendling Light Answer Guide

NSET 110

Bending Light

Name: ________________________________________

Computer Setup: Access the URL http://phet.colorado.edu/en/simulation/bending-light and start the “Bending Light” simulation by clicking on the green “Run Now!” button.

Phase I: Exploration

1. Click on the yellow “Reset All” button at bottom right.

2. Click once on the red button on the laser at upper left. Do not move the laser. You should see a red ray of light from the laser that strikes the boundary between the white and blue areas. This segment, from the laser to the boundary, is called the incident ray.

3. Click and drag the round protractor from the Toolbox and place it in the middle of your screen. Adjust its position to accurately measure the angle between the normal (vertical dashed line) and the incident ray that comes out of the laser.

This angle should be 45°. If you are not seeing that, or you are not sure, ask your teacher to check the position of your protractor.

4. Also measure the angle of the reflected ray (the ray headed up and to the right, also in the white part of the area). Record that angle in the following table.

Click and drag the laser to change the angle at which its ray hits the boundary of the blue and white areas. Record the angle of both the incident ray and the reflected ray. Do this for several laser positions.

1. How Is the reflected ray angle related to the incident ray angle?”

Select the tab “More Tools” at the top of the simulator, and click on the yellow “Reset All” button in the lower right. Press the red button to turn on the laser.

7. Click and drag the “Speed” meter from the Toolbox, placing its point on the incident ray. Move the speed meter to different points on the incident ray (make sure to keep it on the incident ray, between the laser and the horizontal boundary).

8. Move the speed meter to the reflected ray, and measure the speed at various points along that section.

2. How fast is the reflected ray?

9. Now move the speedometer to the ray that is below the boundary, in the bluish area. Measure and record its speed.

In the gray “Material” boxes on the right side, there is a text box labeled “Index of Refraction (n)” where you may enter numbers. In the lower one, choose “Custom” from the drop down menu, then enter a value from 1.00 to 1.60, and measure the speed of the refracted ray.

Record the results in the following table, and repeat for other values of n.

3. How is the index of refraction (n) of a material related to the speed of light in that material?”