EXPERIMENT 10.1
VISIBLE LIGHT
STUDENT INFORMATION
PURPOSE:
To observe the visible light spectrum and understand how white light can be separated into its component colors.
BACKGROUND:
Visible light is a small portion of the electromagnetic spectrum that human eyes can detect. When white light (like sunlight) passes through a prism or water droplets, it separates into different colors based on their wavelengths, creating a rainbow effect. This phenomenon is called dispersion. The colors of the visible spectrum, from longest to shortest wavelength, can be remembered using the mnemonic "ROY G. BIV" (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
In this experiment, you will create your own rainbow by using water as a prism to separate white light into its component colors. This demonstrates how rainbows form in nature when sunlight passes through raindrops in the atmosphere.
MATERIALS:
- A shallow pan (a glass baking dish works well)
- A small mirror
- Water
- A white sheet of paper or a white wall
- Direct sunlight or a bright flashlight
QUESTION:
How can water be used to separate white light into its component colors?
PROCEDURE:
- Fill the shallow pan about halfway with water.
- Place the mirror in the water at an angle (approximately 45 degrees), with part of the mirror above the water's surface.
- Position the pan so that direct sunlight (or flashlight) hits the submerged part of the mirror.
- Hold the white sheet of paper or position yourself so you can see the reflection on a white wall.
- Adjust the angle of the mirror and the position of the paper until you see a rainbow spectrum appear.
- Observe the colors in the spectrum and record them in order in your data table.
- Try changing the angle of the mirror or the distance of the paper from the mirror. Record how these changes affect the rainbow.
DATA:
| Colors Observed (in order) | Effect of Changing Mirror Angle | Effect of Changing Paper Distance |
|---|---|---|
VIDEO DEMONSTRATION:
Light Dispersion Through a Prism
What to Observe:
- White light entering the prism
- The separation of light into different colors (dispersion)
- The order of colors in the spectrum: Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROY G. BIV)
- How the angle of the prism affects the dispersion
ANALYSIS QUESTIONS:
-
What colors did you observe in your rainbow, and in what order did they appear?
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How does this experiment demonstrate the wave nature of light?
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Why does white light separate into different colors when it passes through water?
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How is this experiment similar to the formation of rainbows in nature?
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Based on your observations, which color has the longest wavelength and which has the shortest?
CONCLUSIONS:
Summarize what you learned about the visible light spectrum and how white light can be separated into its component colors. Explain how this relates to the wave nature of light and the concept of wavelength.