Exploration 38.2: Diffraction Grating

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This animation models a diffraction grating that is a series of parallel slits in a material.  You can change the wavelength of the light as well as the slit spacing and see the first- and second-order maxima (position is given in centimeters and angle is given in degrees).  Restart. 

First, consider different colors of light passing through the grating.

1. What happens when you increase the wavelength? 
2. What happens when you decrease the wavelength? 
3. Why do you see the results in (a) and (b)?  Explain in terms of the interference between waves passing through the grating.

Now, consider the effect of the spacing between the slits in the grating.

4. What happens when you increase the number of slits per millimeter (decrease the spacing between slits)?
5. What happens when you decrease the spacing between slits? 
6. Why do you see the results in (d) and (e)?  Explain in terms of the interference between light waves passing through the grating.
7. Using the movable protractor, verify the relationship found in your textbook between the location of the maxima, the wavelength of the light, and the spacing between the slits.

Exploration by Anne J. Cox.
Script by Anne J. Cox and Morten Brydensholt.
Instructor's Resource CD Edition: Do not post or distribute.
The complete version of Physlet Physics is available as a text with CD; Physlet Physics can be bundled with this Prentice Hall textbook.
© 2004 by Prentice-Hall, Inc. A Pearson Company