Color, Light, and Spectra Lesson Plan

Materials:

• 2 Sheets of light sensitive paper

• Objects of various shapes that might cast shadows.

• Convex lenses with focal lengths 3 to 5 inches, one for each pair of students

• Sheets of white paper, one for each pair of students

• Rulers, 12 inches, one for each pair of students

• Diffraction gratings, one for each student

• 4 to 7 different colored light emitting diodes, L.E.D, and power supply

• 1 red laser

• 1 green laser

• 1 compact disc (blank)

• 1 propane tank and Meeker burner

• table salt (sodium chloride)

• dietary salt (potassium chloride)

• cupric sulfate

• strontium nitrate

• iron powder

Light Sensitive Paper

Procedures:

1. The class is divided into two groups.

2. Distribute one sheet of photosensitive paper (photographic paper) to each group.

3. The students are instructed to place items on a piece of photosensitive paper to produce a reverse shadow.

4. The students are asked to place the paper with the items in a bright place by a window or, if the weather cooperates, outside.

5. At the end of the period, the paper is retrieved and the objects removed. The light made the paper darker and where the objects were placed, the paper is lighter.

Making a Camera

Procedure:

1. The use of a convex lens, light source such as a window, and blank sheet of paper, one can demonstrate how a camera works.

2. Distribute the supplies.

3. Allow the students time to experiment with the procedure.

4. When the students have made the camera, demonstrate the measuring of the focal length. Example: Measure the distance between the lens and the paper.

5. Record the various focal lengths.

Introduction to Diffraction Gratings

Procedure:

1. A diffraction grating is distributed to each student.

2. A source of artificial light, such as the room lights or an overhead projector light, work well to have the students view.

3. The students view the artificial light through the diffraction grating.

4. The students view daylight through the diffraction grating and compare it to artificial light.

5. Discuss the differences in the resulting spectra.

6. Darken the room by pulling the shades and turning off the interior lights.

7. Turn on the L.E.D.s one at time and have the students view spectrum of each L.E.D.

8. The students call out the color of the L.E.D.s as it appears to their eyes without the diffraction grating.

9. The students then view the L.E.D.s with the diffraction grating.

Diffraction Grating and Lasers

Procedure:

1. A red LASER is shined on the ceiling.

2. The students view the red laser through the grating.

3. A green LASER is shined on the ceiling.

4. The students view the green laser through the grating.

5. Since a LASER is pure light there is no spectrum but only dots appear through the grating.

6. Bounce one of the LASERs off of the compact disc. Show that the disc will diffract the light also.

7. Point out that the term LASER is an acronym for “Light Amplification by Stimulated Emission of Radiation”.

Diffraction Grating and Fireworks

Procedure:

1. Ignite the propane (Meeker) burner and tip to a 45 degree angle.

2. Some of the respective chemicals are sprinkled into the flame (the flame is about 2000 degrees F.

3. Each chemical is sprinkled into the flame twice, once to see the color without the grating and once to see the spectrum with the grating.

4. Ask the students what colors they see with the grating.

5. Mix the chemicals and sprinkle on the flames.

6. The students are quizzed on the names of the chemicals and the colors they produce in the flame.

7. Explain that fireworks manufacturers the chemicals into the fireworks to display these same colors.