Activity Description

The premise is that a student will shine red coherent light on a series of double slits with different spacing. The spacing will be about 1000 nm, 2000 nm, 3000 nm, and 4000 nm. The students will rank the width of the interfence patterns based on the spacing of the slits.

Target Conceptual Difficulty

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

PowerPoint

Ranking Task - Double Slit Pattern

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 adjust the spacing of the source and they are to predict how the spacing of the interference pattern will changes as the spacing is increased. As the spacing is increased, the effect is not instantaneous ion the screen, you need to a llow 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

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