What causes color in rainbows?

1. Students will be able to draw a picture of their observation that light bends or is refracted when it passes through different kinds of transparent materials.
2. Students will be able to separate white light into it's different colors using a prism.
3. Students will be able to define the vocabulary words: absorb, reflect, & refract.
4. Students will be able to recall the order of the visible light spectrum by using the acronym ROY G. BIV, which stands for red, orange, yellow, green, blue, indigo(dark blue), and violet.
5. Students will be able to explain why different colors are seen.
6. From their observations, students will generalize that light is reflected and is absorbed by different types of matter. (eg. Black paper will absorb all of the wavelengths of light; white paper will reflect most of the wave lengths; and red objects will absorb all but red waves.)

Energy from the sun that reaches the Earth, travels in waves. This energy comes in different wavelengths. Gamma rays, x-rays, ultraviolet, infrared, visible light, microwaves, and radio waves are all part of the electromagnetic spectrum.
Humans can only see the portion of this energy spectrum we call visible light. Visible light is made up of different colors. Each different color has a different wavelength.
When light passes from one transparent material through another of a different density, it is bent or refracted. Different colors or wavelengths will bend differently. That is why when white light passes through a prism, different colors of the spectrum are separated. Since these colors are made of waves of specific length, they will always be separated in the same order. An acronym used to remember this order is ROY G. BIV, which stands for red, orange, yellow, green, blue, indigo(dark blue), and violet.
Light waves can be absorbed or reflected by matter. When waves are absorbed, the energy is transferred to the matter. When black objects are left in the sun they warm. Black objects will absorb all the colors of white light . This absorbed light energy changes to heat energy. Whether light is absorbed or reflected depends on 2 factors, the kind of material it strikes and the wavelengths in the light. The color that we see in an object is the wavelength that is reflected. Green objects reflect the wavelength that we see as green, and absorb all the other wavelengths.
In this lesson, students will observe the different wavelengths of visible light by separating them with a prism. They will experiment with absorption and reflection in different types of matter. Generalizations from these experiments should help them understand how some energy waves from the sun pass through the atmosphere, strike the Earth and are reflected into space, while infrared energy waves are absorbed by carbon dioxide and other greenhouse gases.


Students work in cooperative groups of 4

per student
per group
clear glass of water
4 sheets of 9x12 construction paper
-white, black, red, green

-Introduce the lesson by posing the following questions
1. What is light?
2. Is white light made up of separate colors?
3. What causes a rainbow on a rainy day?
4. Why do we see different colors?
5. How does light interact with different kinds of matter?
6. How can studying light help us understand the greenhouse effect?

1. Have each group of students fill a clear glass with water and place a pencil in it
a. Students are to record their observations and draw a picture of what they see. -Does the pencil look straight or bent?

1. Have the students fold the 4 pieces of construction paper in 1/2 and prop them on the table in front of them.
b. Students shine flashlight through the prism so that it projects a spectrum of color onto the white paper.
- students draw spectrum on their work sheet.
c. Repeat step b above using the other color backboards.


1. Go over the worksheet and discuss answers

Check the student's answers to the work sheet. Do they understand the properties of light? Do they know the difference between reflect, refract, and absorb?

Have students experiment with mirrors and light.
Demonstrate the behavior of waves by placing a clear pan of water on a overhead projector and dropping a pebble in to make waves.
If a hose and spray nozzle are available, take the students outside and create rainbows in the sunlight. compare the order of the colors to the prism experiment.

Relate this activity to the greenhouse effect.
Energy from the sun comes in a wide range of wavelengths. We can only see a small portion of the electromagnetic spectrum. This band of wavelengths contain the colors that we can see. It is referred to as the visible light spectrum. The atmosphere is transparent to some of the sun's energy waves. The ozone layer in the atmosphere absorbs harmful ultraviolet radiation. The energy that does make it through the atmosphere,heats the Earth's surface. This warmed surface radiates infrared energy waves back through the atmosphere. Some of this infrared energy is absorbed by carbon dioxide and other greenhouse gases. The warmed atmospheric gases radiate heat back down to the surface keeping it comfortably warm.


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