Activity Description

In this activity a "student" makes the following statement Student: “If I change the light from red to green, the distance between bright spots won’t change because only the slit spacing affects the interference pattern.” The students are asked what if anything is wrong with the "students'" statement. the question is resolved by changing the wavelnght of the light and viewoing its effect on the interference pattern.

Target Conceptual Difficulty

Inability to describe the change in the pattern as the slit spacing and the wavelength change.

PowerPoint

What if Anything is Wrong Task - Dependence of 2 slit Pattern on Wavelength

Simulation

http://phet.colorado.edu/new/index.php

Click on the button marked "Play with Sims...>". On the page that appears click in the left frame on the link "Light and Radiation" and then click on the icon or link for Wave Interference. Click on the light Tab, then click on the Two Lights radio button. Click on the Show Screen button and the click on the Intensity Graph button to make it easier to see how the pattern changes as the spacing between the light sources change. Adjust the Light Spacing to about 1000 nm. At this point the simulation should look like the following.

Presentation Notes

Once the simulation is set up, explain to the students that you will change the wavelength of the light by dragging the slider. Once the wavelnght is changed, the effect is not instantaneous ion the screen, you need to allow a few seconds for the interference pattern to catch up.

Student Results

No student results are available for this activity.

Pen and Paper Actvivities

Pen and Paper version of this activty

Follow up tipers from homework assignments, test reviews and test items