Materials

• Hydrogen tubes and other gas tubes with an excitor (located over Dr. Hill’s desk)
• “Rainbow glasses” (3-D glasses found in the left bottom drawer or blue bin over Dr. Hill’s desk)
• Colored filters (found in belly drawer of desk; filter paddles in blue bin)
• C-spectrum lens (available in blue bin)
• Sheets of C-spectrum film (on model boxes over Dr. Hill’s desk)

Procedure

1. Observation of Visible Spectrum:

• Have students put on the “rainbow glasses.”
• Direct them to look at a single point source of light or lamp. They should see the visible spectrum.

1. Using Colored Filters:

• Place a colored filter over the light source.
• Ask students to identify which line of the spectrum has disappeared.

1. Hydrogen and Gas Spectra:

• Have students observe the distinct patterns of light generated by hydrogen and Kr/Hg/O2 spectra using the glasses.

Teacher Lesson Plan: Diffraction

Objective

To understand the origins of colors in light, how colors combine to create various shades (including white light), and the effect of color filters on light.

Materials

1. Overhead projector and three half-sheets of black construction paper (4-1/4″ x 11″)
2. Diffraction grating (4″ x 4″; source: Rainbow Symphony)
3. Diffraction grating glasses (Rainbow Symphony)
4. Colored gels or filter materials
5. Light bulbs: 40 watt clear (preferably cooler), green, blue, red party bulbs, inexpensive bug light, small fluorescent night light

Procedure

1. Projecting White Light:

• Position the overhead projector at half the normal distance from the screen.
• Project white light onto the screen and discuss its makeup.
• Use the diffraction grating to create a color wash on either side of the projection window.
• Place the black construction paper to allow only a narrow strip of light through, noting the colors that emerge.

1. Using Color Filters:

• Lay colored gels across the narrow slot to observe the effects of color filters on the projected light.

1. Diffraction Grating Glasses:

• Distribute diffraction grating glasses to each student.
• Have them observe light from various sources (ceiling fixtures, windows, light bulbs) and log their observations.

Discussion Points

• Explain the differences in light appearance and how various colors bend through the diffraction grating.
• Discuss concepts of diffraction vs. refraction.

Resources

Diffraction Grating Materials

• Rainbow Symphony Inc.
• 6860 Canby Ave. #120, Reseda, CA 91335
• Tel: (818) 708-8400
• Fax: (818) 708-8470
• Toll Free: (800) 821-5122
• Email: rainbowsymphony@rainbowsymphony.com

Activity Workbook

• Color Analyzers
• GEMS/Lawrence Hall of Science, University of California, Berkeley, CA 94720
• Tel: (510) 642-7771

Background Information

• Sir Isaac Newton discovered that light consists of a spectrum of seven distinct visible colors, always appearing in the same order (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
• Understanding that objects appear colored based on the light they reflect can help explain color perception.
• Note: Never look directly at the sun as it can cause eye damage.

©2007 Rainbow Symphony, Inc.