Use a diffraction grating to measure light from a sodium lamp

Your job is to use a diffraction grating to measure

• wavelengths of light emitted by sodium atoms

Remove the diffraction grating from the optical bench and hold it carefully in your hand, a few inches in front of one of your eyes. Look through it at the spot formed by a laser on the wall.

1. What do you see?

Now, hold the grating in front of your eye as you look at the lamp sitting on the desk at the front of the room.

2. What do you see now?
3. How can you use this technique to measure the wavelength of light emitted by the lamp? Draw a picture to explain.
4. Measure the wavelength of the yellowish light emitted by the lamp. Show all your measurements, including uncertainties. Derive the uncertainty in wavelength of the light.
5. What is the actual wavelength of this light? Is your value consistent with the actual value, within the uncertainty?

Hint: Sample Problem 36-6

Copyright © Michael Richmond. This work is licensed under a Creative Commons License.