FINGERPRINTS OF LIGHT
Grades 6-8

In this lesson, the students should learn that light travels as waves, which can be compared by measuring wavelengths. Utilizing spectrometers, the students should learn how gases emit specific emission lines, like fingerprints, which can be utilized to identify lighted tubes, or bulbs, containing a mystery gas. Additionally, the students should learn that the color of an object depends on the color of light absorbed and the colors of light reflected.

3-2-1 Classroom Contact #24: Light and Color: Living Color Minds On Science #3: Properties of Light Starfinder #24: Fingerprints of Light

Students will be able to:

• describe how visible light is a form of electromagnetic energy
• demonstrate how primary lights are used to create other colors
• identify that white light is a mixture of all the colors of light
• graph the visible spectrum, as created utilizing a prism
• state the relationship between energy emission, color, and wavelength
• explain the relationship between the color of an object and the lighting conditions under which it is seen
• use a spectroscope to identify emission lines and compare different lights
• and use emission lines to identify an energized mystery gas

Teacher demonstration:

• 1 red cellophane sheet
• 1 green cellophane sheet
• 1 blue cellophane sheet
• 1 teacher-drawn picture of a person in lightly colored primary colors
• Pale lavender piece of material (other colors may also be used)
• Various light bulbs, such as sodium vapor, mercury vapor, fluorescent, incandescent, halogen, or colored lights
• 1 electrical power plate
• 1 plug in outlet-adapter per light bulb
• 1 prism
• 1 flashlight or overhead projector
• 1 Spectrum Analysis Chart
• 1 sheet of red, blue, and yellow construction paper

Per individual:

• 1 Spectra Vision worksheet
• 1 Mysterious Mixed-Up Colors worksheet
• 1 Spectroscope
• 1 Fingerprints of Light worksheet
• 1 of the following crayon/marker colors: red, blue, green, orange, violet, blue, indigo, cyan (blue-green), magenta, yellow
• 1 piece of yarn, approximately 3 feet long

Per group of 4 - 6 students:

• 3 flashlights
• 1 red cellophane sheet
• 1 green cellophane sheet
• 1 blue cellophane sheet
• 3 rubber bands
• 1 sheet of white construction paper

Mysterious Mixed-Up Colors Distribute the flashlights, cellophane sheets, rubber bands, white construction paper, and Mysterious Mixed-Up Colors worksheet. For best results, perform this activity in a darkened room.

Note to the Teacher: Depending on the quality of the cellophane, it may need to be doubled to achieve expected results. Rubber band the cellophane sheets onto the lighted end of the flashlights. Prior to combining the beams of light, the students should predict the resulting color combination. After combining the light rays, the students should record the results on the Mysterious Mixed-Up Colors worksheet. Combine colors in the following order: red + blue (magenta), blue + green (cyan), red + green (yellow), red + blue + green (white). Conclude the discussion by identifying red, blue, and green as the primary colors of light.

Spectra Vision Distribute the Spectra Vision worksheet. The students have just learned how white light is a result of mixing the primary colors of light. In this activity, the students will identify the visible spectrum and compare each color with its corresponding wavelength. Demonstrate how a prism can be used to refract light into the visible spectrum. Students should color the appropriate box on their worksheet and compare each color to the corresponding wavelength. Tie the yarn to the back of each student's chair. Students should use the information concerning wavelength to create yarn waves to illustrate violet, red and yellow/green waves. They should discover that as the frequency increases, the wavelength decreases; therefore, more energy is expended to create a violet wavelength than a red wavelength.

Note to the teacher: Light entering a prism slows down, which causes the white light to refract. As the light leaves the prism, the colors are bent at different angles thus producing the rainbow of colors. If a prism is unavailable, a clear glass of water may be placed on the overhead projector to obtain the same results as passing light through the prism.

The focus for viewing is a specific responsibility or task(s) students are responsible for during or after watching the video to focus and engage students' viewing attention. In the previewing activities, the students learned that the wavelength affects the resulting color.

Secondly, they learned that white light is a combination of all the colors in the visible spectrum. In the viewing activities, the students should learn how the color of an object depends on the color of light absorbed and reflected. Additionally, the students should learn how emission lines are created and utilized to identify energized gases.

BEGIN the video 3-2-1 Classroom Contact #24: Light and Color: Living Color at the cartoon title "Catch This." The audio cue is: "You're walking down the street minding your own business and the whole time your pants are being hit by light." The students are to view this segment to learn why we might perceive an object as being red in color.

RESUME and STOP the video after the verbal cue: "Red light reflects off the red pigment and hits you straight in the eyes." Review the information presented in the video by asking the students to explain why an object might appear to be red.

Use the teacher-drawn figure and the colored cellophane sheets to demonstrate how colored lights affect the appearance of an object.

Note to the teacher: A red object will still appear to be red under the red cellophane because it is reflecting red light. However, under the blue or green cellophane, a red object will appear to be darkened, or black, due to the fact that it cannot reflect blue or green light and red light cannot be reflected due to its absence.

Similar results will occur with green and blue colored items. The same results can be noted by placing a multi-colored piece of material against a background and projecting a light beam resulting from a colored cellophane sheet placed on an overhead projector.

BEGIN the video Minds On Science #3: Properties of Light, where Tif and PJ enter Rollo's lab. The verbal cue is "What happened to you?" In this segment, the students should learn that Tif is upset because she thought she bought gray pants, but they turned out to be lavender. The students are to view this segment to determine the problem with Tif's new purchase.

RESUME and PAUSE after Rollo asks "What do you think made the pants change color?" The students are to formulate hypotheses based on their current information. They should view the next segment to compare their predictions with those of the characters in the video.

RESUME and PAUSE after the verbal cue "How can we find out what made the pants change color?" The students are to formulate hypotheses and then compare their predictions with the scientific method of the characters in the video.

RESUME and PAUSE after the verbal cue "PJ, hit the light would you?" In this segment, Rollo will demonstrate how different lights affect the appearance of Tif's pants. Before viewing, have students predict the color of her pants when viewed under a light from the Bahama Shop (gray). Additionally, the students should view to observe additional color changes of her pants, which result from different lighting conditions. RESUME and PAUSE after Tif's verbal cue "They're sort of gray. So it wasn't Jeffrey. It must have been the lights" and Rollo's response "Well, let's look at them under some different lights."

RESUME and PAUSE after Rollo's verbal cue "It's called a spectrometer." The students are to view this segment to learn what a spectrometer is and how it is utilized to provide information about different lights.

Note to the teacher: Distribute the Fingerprints of Light worksheet. The students will use crayons or markers depicting the colors of the visible spectrum. They will draw the three different light patterns displayed in the viewing segment. There are no verbal cues to indicate the pause points. Therefore, it is important for the teacher to carefully view this segment and to pause as each new light pattern is presented. The students will utilize these light patterns to learn about emission lines and identify the mystery gas in each tube.

RESUME and STOP after the following dialogue: Tif: "Rollo, we did it." PJ: "What did we do?" Mark: "We drew these lines, but we don't know what they are." Rollo: "Mark, science is a long and winding road of discovery."

BEGIN Starfinder #24: Fingerprints of Light at the verbal cue "My fingerprint, there's not another one like it in the entire world." The students are to view this segment to learn how light can have a fingerprint.

PAUSE after the verbal cue "Each has a unique fingerprint of light that can help scientists identify it. We'll show you how on Science Links." The students are to view the next segment to learn the names of the scientists who began to study the spectrum of light during the 1860s.

RESUME and PAUSE after the verbal cue "In 1860, Gustav Kirchhoff and Robert Bunsen began to look at the spectrum of light emitted by hot objects." The students are to view the next segment to learn techniques utilized by Kirchhoff and Bunsen and how their results compare with the use of a prism.

RESUME and PAUSE after the verbal cue "When light goes through, it's broken up into its component colors just like when light goes through a prism." Discuss how the results of heating a solid object are similar to the use of a prism to identify the spectrum. In the next segment, the students should learn the name of the spectrum resulting from a solid object (continuous).

RESUME and PAUSE after the verbal cue "The spectrum from solid objects is called a 'continuous spectrum.'" The students are to compare the light patterns they drew with the continuous spectrum. Although they may note the use of similar colors, they should state that their patterns aren't continuous. The next viewing segment illustrates how absorption line spectrums are created and can be used like fingerprints.

RESUME and PAUSE after the verbal cue "They found that every different gas and every different element they looked at had its own distinctive pattern of lines. These lines were just like fingerprints." The students should explain how an absorption line spectrum is created. They should compare their drawings with this type of pattern. They should note that there are bands of missing colors. Have the students hypothesize about the identity of the missing colors. The students should view the next segment to learn about the emission line spectrum. Have the students speculate as to the appearance of this type of line spectrum, then view to compare their theories to the actual item.

RESUME and PAUSE after the verbal cue "The colors which have disappeared as the light travels through a gas are exactly the same colors that were seen in the emission spectrum. Why does the spectrum of light look like this? Kirchhoff and Bunsen never found out. Only in this century was it discovered where the light comes from." The students should compare their predictions and their drawings with the emission line spectrum presented. Discuss the techniques utilized to create this type of spectrum. The students are to view the next segment to learn how the structure of the atom, specifically electrons, create this type of spectrum.

RESUME and PAUSE after the verbal cue "Electrons are basically a lazy bunch. They stay at the lowest energy level possible. Forms of energy, such as heat and light, can boost the low electrons to higher levels. But being a lazy bunch, these electrons get rid of the extra energy as soon as possible and move back to their resting state, giving off energy in the form of light as they return to their lower level." Role play the information presented in this segment. Have student volunteers stand behind their chairs. At your command, have the students move 3 paces to their right, decide they'd rather be seated, and return to their original chair.

RESUME and STOP after the verbal cue "Different amounts of energy correspond to different wavelengths of light. High energy light appears blue, while light at low energy levels appear red. . . Therefore, each has its own unique pattern of emission lines, its own fingerprint." Utilizing the red, blue, and yellow construction paper, role play the information presented in this segment. Have the students stand behind their chairs and face the teacher. When a red sheet of construction paper is displayed, move one pace to the right, pause, and return to the original position. When a yellow sheet is displayed, students move two paces to the right, pause, and return to the original position. If a blue sheet is displayed, move 4 paces to the right, pause, and return to the original position. Repeat as is necessary.

RESUME and PAUSE Minds On Science #3: Properties of Light exactly where it was previously stopped. The verbal cue is "Take a look at these." (He is referring to a Spectrum Analysis Chart. Display one of these charts after you pause the video.) Before resuming, remind students that Rollo said science was a long and winding road of discovery. Now that the students can identify an emission line spectrum, they will compare their emission drawings with the Spectrum Analysis Chart and identify the three mystery gases.

RESUME and PAUSE after the verbal cue "OK, so these lines tell us what was in the light bulbs. What makes the colors in the first place?" This explanation was presented in Starfinder #24: Fingerprints of Light. Ask a student to explain the answer to Tif's question. If no one is able to correctly reply, VIEW the next segment as a review. However, if students understand the electron orbital concept, FAST FORWARD through the explanation and the laser segment, then begin after Tif, PJ, and Mark return to Rollo's lab. The verbal cue is "Someone, please, just tell me why my pants change color!"

In light of their new discoveries, have students predict why the pants changed colors, then have them view the segment to compare their explanations to those presented in the video.

RESUME and STOP after the verbal cue "So, my pants change color because of the lights in the store."

Screw various bulbs into outlet adaptors, like those Rollo used in his demonstration. Light each bulb. Have students observe the color and type of light being emitted. The students should use a spectroscope to view the spectrum patterns. After observing the light, have students predict how the lighting will affect various colors of material. Darken the room and test predictions. The students can use crayons to record and compare their observations.

Invite a sign maker to your classroom to learn about how different gases are used to create signs.

Use the Internet to connect with scientists who use high resolution spectrographs to learn about stars.

Write to your local hospital for the names of resident radiologists or technicians to contact concerning information about X-rays.

Write to television manufacturers to learn how television uses primary colors to create the various colors seen on the screen.

Invite a local geologist to the classroom to demonstrate how black lights are used to identify certain fluorescent minerals.

Write to a dermatologist or sun screen company to learn about the harmful affects of ultraviolet rays and how to protect yourself from its damaging effects.

Visit a local theater or high school to learn about how lighting is used to create special effects and moods.

Use the Internet to learn how satellites use the spectrum to identify trouble areas in crops and to indicate weather information.

Art: View remaining segments of 3-2-1 Classroom Contact #24: Light and Color: Living Color to learn how to paint pictures with light.

Art/Science: Create colored shadows by focusing the primary colors of light onto a white wall. Move your hands between the light source and the wall. Your results will be to create colored shadows.

Social Studies/Science: View 3-2-1 Classroom Contact #26: Refraction: Facts of Light to learn how a lighthouse utilizes mirrors and prisms to create their powerful lights.

Science/Language: Use light-sensitive paper and various sun blocks to test how effectively they block harmful ultraviolet rays.

Develop an ad campaign to sell a fictitious sun block lotion.

Art/Language: Research to discover how the ozone layer protects us from ultraviolet radiation and how CFCs affect the ozone layer. Use this information to create a poster and an ad campaign to protect the ozone layer, or write a persuasive paper to explain why products containing CFCs should be banned.

Science/Language: Research to discover the relationship between infrared wavelengths and the greenhouse effect. Use plastic baggies, thermometers, baking soda, vinegar, and small containers to demonstrate the relationship between carbon dioxide and the greenhouse effect. Research to discover the greatest contributors of carbon dioxide into our atmosphere, then write a persuasive paper to convince others to modify their behavior to lessen carbon dioxide emissions.

Language: Write a science fiction story about the use of lasers to discourage alien invasions. Or write a fairy tale or myth to explain why rainbows are created.

Math/Language: Construct a graph to illustrate the relationship between the type of lighting and the amount of light per unit of energy (lumens). Incandescent lights provide about 20 lumens per watt, fluorescent lights provide 70 lumens per watt, mercury vapor lamps provide 50 lumens per watt, metal halide lamps provide 90 lumens per watt, and high-pressure sodium lamps provide 110 lumens per watt. Compare the information on the graph and use it to write a persuasive paper to convince your community to install high-pressure sodium vapor street lamps.

Master Teachers: Valerie Lyle and Kathleen Shannon