Extra Credit: Measure the wavelength of laser light

Measure the wavelength of a laser's light.

This project may be done by teams of 1-2 individuals. The goal is to measure the wavelength of light emitted by a laser.

Under no circumstances should you aim a laser beam into your eyes, or anyone else's eyes.

There are several ways you might proceed. In every case, you may procure the materials you need --- a laser, little optical bench, and some slides with slits --- from the Physics Department stockroom. If you have questions or cannot get the equipment you need, please talk to me.

You might try to use the pattern of light produced by the interference of light passing through a pair of slits. You'll need to project the light onto a screen, measure the distance to the screen, and measure the distance between the central and first (or second, or third, or ...) maxima. You'll need to know the distance between the slits.
You may also try to send a light beam through a single slit and measure the distance between the primary and secondary maxima in the diffraction pattern. Again, you'll need to know the distance between the slit and the screen. You'll need to know the width of the slit.

There may be other methods to measure the wavelength of light, too. Perhaps you may think of some method which involves refraction... You may adopt any method you wish, as long as you describe clearly how your method works.

Once you've made the measurements and calculated the wavelength of light, try to look up the accepted value for the laser in question. Most lasers use a mixture of He-Ne (helium-neon) gas to create a beam of red light with wavelength between 630 and 680 nanometers. If there is a large difference (more than 10 percent) between your value and the accepted one, try to explain it.

Submit a report which contains a description of your method, with a clear drawing and all relevant dimensions. Include the data for your experiment, and all calculations. You may also include interesting items you discovered during the course of the procedure.

This page maintained by Michael Richmond. Last modified Apr 29, 1998.