Visible Light

Lesson Plan - Get It!

Audio:

In the previous Related Lessons, found in the right-hand sidebar, you learned that each light wave is grouped into one of seven categories.

The seven groupings are shown in the picture above.

• Do you remember how scientists decide into which category a light wave goes?

Tell your teacher or parent.

Light waves are grouped according to the amount of energy they possess. Humans are only able to see one type of light wave.

• Do you know which light wave humans can see?

Tell your teacher or parent.

Humans can see visible light. You can remember this because visible light is visible to humans!

In this lesson, you will learn more about visible light and how it allows you to see colors. To start, you need a prism. If you do not have a prism, you can purchase an inexpensive prism from a hobby store or online, or make the makeshift one in the video below.

When you have a prism, point a flashlight at the prism. Try holding the prism and flashlight at different angles to see what happens. Also, try holding the prism up towards a light. Discuss your observations with a teacher or parent.

If you are unable to purchase a prism, or just to reinforce what you've observed, watch the following How a Prism Works to Make Rainbow Colors (RimStarOrg) video:

• When you were investigating light with the prism, did you see a rainbow?

If so, you saw all of the colors of the visible light spectrum.

White light is all the colors of the visible spectrum together. When white light from the flashlight enters the prism, the light is refracted.

When the light is refracted, you can see all the colors that make visible light. The colors that make up visible light include red, orange, yellow, green, blue, and violet. Indigo used to be a part of the visible light spectrum, but scientists no longer include this color in the spectrum.

The following image shows the light waves associated with each color on the visible light spectrum. Discuss your observations with your teacher or parent.

^{Image by Rubber Duck, via Wikimedia Commons, is licensed under the CC BY-SA 3.0 license.}

• Did you notice that red has the longest wavelength and smallest frequency, while violet has the shortest wavelength and greatest frequency?
• Based on this information, which color on the visible spectrum has the most energy? The least energy?

Discuss the answers with your teacher or parent.

Remember, the greater the frequency, the greater the energy. Therefore, violet light has the most energy and red light has the least energy.

To learn more about why humans can see visible light, and how your eyes interpret colors, watch this How Do We See Color? video by SciToons:

After watching the video, explain to your teacher or parent what rods and cones are, and how they help you see the visible spectrum.

Now, move on to the Got It? section to learn more about the way you see and perceive colors.