University of Virginia
Physics Department

## Visible Spectrum

A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.9

Objectives

Students will

• Compare different spectrums given off by various light sources around them.

Motivation for Learning

Driving Question

How do visible spectra of different light sources compare?

Background Information

### Student Activity

Materials

• Spectroscopes with scale
• Colored pencils
• Incandescent light source
• Fluorescent light source
• UV light source
• Mercury vapor light (in most gyms)
• Sunlight source
• Any other light sources available

Check with your school engineer about what different light sources are available in your school. Most gyms have mercury vapor lights and some schools have sodium lights also. Incandescent lights can be slide projectors or overheads. Be careful to eliminate light sources contaminating each other. You may want to have only one light source on at a time and all students do that one and then turn it off and do another one. Make sure that you block all outside light from entering.

Resources:

Procedure

1. Point the slit of the spectroscope toward the light source. Get the spectrum to line up with the scale in the scope.
2. Draw a picture of the spectrum that you see in the spectroscope. Draw the picture carefully, showing the relative sizes of the colored bands and any bright lines that you may see. Use the scale to help you determine the relative sizes of bands.
3. Repeat steps 1-2 for all of your light sources. NEVER LOOK DIRECTLY AT THE SUN WITH THE NAKED EYE, you may look next to the sun for your spectrum.
4. When you have finished with all of your unfiltered spectrums, get a colored filter and hold it up to one of the light sources and draw what the spectrum looks like now.

Data Sheet

Light source:

Light source:

Light source:

Light source:

Light source:

Light source:

Light source:

Light source:

Students with Special Needs

All students should be able to participate in this activity. Some students will not be able to see the colors, these students may still copy the colored drawings form another student and will be able to answer the questions. Having special needs students label the colors with the letters ROYGBV will be helpful in many cases.

Click here for further information on laboratories with students with special needs.

Assessment

1. Which spectra are the most similar? The most different?

2. What does the filter do to the light?

3. What is the difference in the spectrum between incandescent and fluorescent light?

4. Which spectrum had the most even distribution of colors?

5. Which spectrum had a bright purple line at about 4 ½ and a bright green line at about 5 ½?

6. Which spectrum did you feel was overall the brightest?

7. What was the independent variable in this experiment?

8. What was the dependent variable in this experiment?

9. How could this information that certain lights produce certain spectrums be used, what would be an application of this knowledge?

1. Will vary depending on what light sources the students use.
2. The filter should eliminate all colors except the one that is the same as the filter.
3. ?
4. Will vary depending on what light sources the students use.
5. Fluorescent
6. Will vary depending on what light sources the students use.
7. The different types of light.
8. The spectrum.
9. Determination of elements in space due to the light spectrum.