Procedure:

Observe the following precautions and do the following things:

1. The diffraction grating is very fragile. Do NOT touch the grating itself in any way.
2. The mercury vapor light emits a considerable amount of radiation in the ultraviolet region. This can cause severe eye damage. Leave the diffusion filters on the source at all times, even when taking measurements. Wear protective UV goggles at all times during the lab.
3. The potential across the discharge tubes is about 5000 volts. Do not touch the discharge apparatus when the power is on.

4. Align the diffraction grating so that it is nearly as possible perpendicular to the optical path set by the light source, collimator or slits, and telescope. Adjust the telescope to receive parallel light (this can be done by focusing the telescope on an object very far away).

5. For a given source of radiation, measure the angles of each wavelength observed. (The first order spectrum, N = 1, is probably all you will be able to see.)

6. Everyone should take data for H, and He, and one other source.