When light is passed through a diffraction grating, the rays of light are refracted and dispersed, resulting in a spectrum. In this activity we will explore the use of transmission diffraction gratings and the spectra produced by different light sources. The results of the experiments should be recorded for inclusion in a short written report.

• Diffraction gratings mounted in slide holders
• Mirrors
• 8 1/2" x 11" white cards and stands (to be used as projection screens)
• Assortment of light sources: sunlight, laser pointer, white-light flashlight, red LED flashlight, fluorescent light
• Colored filters

You will be given a diffraction grating slide, colored filters, a mirror, a small projection screen and a light source. You will conduct a number of experiments, based on the "Discovery" questions below. Many of the questions require you to compare spectra produced with different types of light sources. In this case, you are encouraged to work with the students sitting next to you, as they will posses different light sources than you do. In addition, some questions require you to compare different prisms or use more than one grating. In this case, you should form a group with the students sitting near you and perform the experiments as a team.

Do keep notes on the results of the experiments, as this information will be included in a short written report, the exact specifications of which will be discussed and determined at the end of the activity session.

• Is a spectrum produced regardless of what angle the light enters the diffraction grating?
• Is a spectrum produced regardless of which side of the diffraction grating the light enters?
• Is a spectrum produced regardless of the orientation of the diffraction grating?
• How does the spectrum produced by sunlight compare with that produced by a white flash light?
• What is the difference between the spectrum produced by sunlight and the spectrum produced by a fluorescent light?
• Does the spectrum produced by a diffraction grating look the same as one produced by a prism?
• How does the spectrum produced by a laser pointer compare with that produced by a white flash light?
• How does the spectrum produced by a red LED flashlight compare with those produced by a white flash light and a laser pointer?
• What happens if you pass light through two diffraction gratings?
• What is the result of passing light through a colored filter before the diffraction grating?
• What happens if you pass light through more than one colored filter before the diffraction grating?
• Can you turn a transmission grating into a reflection grating simply by placing a mirror behind it?