LESSON 2 - What Color is it?
- Identify whether an object reflects or absorbs red, green, and/or
- Reinforce their knowledge of the primary colors of light.
- Create a simple spectral signature.
White file folders or 11"x 14" poster board (1 per
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
Worksheet 2 - answer key
Digital Picture worksheet
Digital Picture answer key
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.
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.
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
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.)
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.
RETURN TO TEACHER'S