Date: December 20, 2000

Grade Level: 6

Subject(s):

• Science/Physics

Duration: Two 50-minute sessions

Description: As a group, students will examine different pictures of the sky and make conjectures about how the sky's color is being produced in each picture. In small groups, students will recreate the colors of the sky with provided materials, recording observations and results. Considering results and observations, students will be asked to determine why the sky is blue and why sunsets are red. Students will explore concepts of traveling light including how light scatters, travels in waves, and produces different colors based on wavelength and size. Students will be asked to relate learned concepts to real world phenomena. 

Goals: Students will develop an understanding of how light travels.

Objectives:

1. Students will learn that the sun emits energy in the form of white light.
2. Students will understand how visible light scatters.
3. Students will observe short wavelengths (blue) and long wavelengths (red) of light.
4. Students will be able to communicate relationships between experimental observations and real world phenomena.

• transparent box or aquarium
• flashlight
• spoon
• 1/2 cup of half & half
• 1 white 3x5 index card (blank)
• Colors of the Sky Worksheet for each student

Worksheet in .pdf format; requires free Adobe Acrobat Reader.

Click the icon to obtain the free Reader.

1. white light - The sun produces light which is made up of all colors of the color spectrum: red, orange, yellow, green, blue, indigo, and violet.
2. scattering -  Light travels in a straight line until it strikes an object. Upon interception, the path and direction of light changes, producing the scattering of light waves.

[ Author's Note: "Our Best Thinking So Far" is a way to assess students' prior knowledge about the topic -- what they know at this point. After the experiment, students can look back and see if their thinking was correct. This strategy is a good motivational tool and confidence builder.]

Challenge Phase:  
"Why is the sky blue? Why are sunsets red? Use the materials that have been given to you (aquarium, flashlight, half & half, index card, and spoon) to recreate colors we see in the sky. What do you notice about the colors that are produced?" Students work in groups of four to recreate the colors of the sky. Each student has a designated job: materials pick-up, dropping half & half into the aquarium, stirring the mixture, and materials clean-up. Students record observations and thoughts on an outlined worksheet of the experiment (see Colors of the Sky worksheet). 

Concept Introduction:
Ask students to share how they recreated the sky and its colors. Update “Our Best Thinking So Far” by writing results and observations on the board. Draw a diagram of the sun and the earth on the board. Ask students, "Considering the results of our investigation and recreations, why is the sky blue and why are sunsets red?" Using the diagram, discuss the path light travels from the sun and what happens when light hits the earth’s atmosphere. Also discuss how light travels in patterns of waves and how the length of each wave affects color. Help students make connections to short wavelengths appearing blue in color and long wavelengths appearing red. 

Concept Application:
Ask students, "What will happen to the colors if we dump more half & half into the tank?" Students should make predictions. Students dump more half & half into the tank and make observations. Ask students, "Comparing our tanks to the real world, what situations might cause the same results?" (Similar situations could include forest fires, pollution, smog, etc.) "Why, during the recent forest fires, did the sky appear reddish in color?"

Assessment: Collect students' worksheets to check for completeness. Students will demonstrate what they have learned through a homework assignment. Ask students to find or draw a picture of the sky. In three sentences or more, students should describe how the color of the sky in the picture is being produced.