LESSON 2 - What Color is it?

Students will:

• Identify whether an object reflects or absorbs red, green, and/or blue light.
• Reinforce their knowledge of the primary colors of light.
• Create a simple spectral signature.

Materials Needed:

White file folders or 11"x 14" poster board (1 per group)

Flashlights (1 per group)

Solid-colored blocks - red, green, blue, cyan (or turquoise), magenta, or yellow

Worksheet 1- What Color is it? (1 per group)

Worksheet 1- answer key

Worksheet 2 - Spectral Signatures (pdf file)

Worksheet 2 - answer key

Digital Picture worksheet (pdf file)

Digital Picture answer key (gif image)

Crayons

Engagement

Ask students "Why is does grass look green to us?" Record their responses. Explain to them that objects absorb and reflect the color of light we see. In this lesson, they will model this concept.

Exploration

Divide students into groups of three. Give each group a flashlight, a white file folder, and 5 different colored blocks. (If you use poster board, have students fold it in half, widthwise.) Have groups stand their folder on the width edge. Tell them to place an object at the vertex of the folder, then shine the flashlight on the object. Students’ task is to identify whether the object reflects or absorbs red, green, and/or blue light. Have students complete the chart on worksheet 1. Tell students to use the "Primary Colors of Light" diagram from Lesson 1 as a guide.

Explanation

When students finish this exercise, discuss their results. Students should observe that an object reflects the color of light that we see and absorbs all other colors.

Continue by discussing students’ answers for the "Think about it" questions. Lead them to understand that white objects reflect all colors of light and black objects absorb all colors of light.

Extension

Explain to students that there are scientists who study the amount of light objects reflect. When scientists study the Earth from space, they look at the color of light reflected. The amount of light reflected describes the characteristic of an object. Using the chart they just created, have the students graph the amount of light reflected by the objects they used in the activity on worksheet 2. The y-axis will be the amount of reflected light and the x-axis will be the red, green, and blue light.

After students complete this, explain that scientists use sensors which look at the amount of light an object reflects, such as a rock or a pond. These sensors give a numeric value for the amount of light reflected, then this data is graphed. The graphs, also called spectral signatures, of different objects such as a rock, water, or a plant are unique. By knowing the "signature" of a particular object, a scientist can identify similar objects over a large geographic area.

Because the amount of light reflected can be represented by numbers, by having just the numbers, we can make an image. Give students the digital picture worksheet. Before creating the digital picture, have students label the intersections of the venn diagram with the corresponding colors. Then, as a class, determine the colors represented by the combinations of numbers. Have students color in the picture using that key. (This activity may also be used for homework.)

Evaluation

Use the "What Color is it?" worksheet to assess whether students understand the combinations the primary colors of light create. Review the answers of the worksheet. In the chart, students should identify which of the red, green, and blue are absorbed and reflected for each object. For example, for a yellow object, red and green light are reflected while blue light is absorbed. Display a few colored objects and ask students to identify whether it reflects or absorbs red, green, and/or blue light.

Tips for Teachers

• Flashlights - Have each student bring in a flashlight for this activity. Or, ask a local company to donate mini-flashlights.
• Blocks - Use small pieces of colored-construction paper.

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