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Course

Explore – Be a Spy of Nature

Why is the Sky Blue?

Purpose: Students will discover why the sky appears blue during the day and red during sunset.

Materials:
1. Glass Jar
2. Water
3. Milk
4. Flashlight
5. Teaspoon
6. Pencil and handout

Procedure:

  • Perform this experiment in a dark room.
    Fill the glass jar (or bottle) up with water. Leave a small amount of room at the top to add milk.
  • Shine the flashlight horizontally through the jar and observe.  Do you see a path of light? Record your observation as Yes or No.
  • Add 3-4 drops of milk to the water. Stir.
  • Hold the flashlight above the jar of water and shine down vertically through the mixture.
  • If the light color does not change, add one more drop of milk and repeat.
  • Record the color of light observed passing through the liquid.
    Shine the flashlight horizontally through the jar and observe a beam of light passing through the liquid.

What’s happening?

The particles of milk in the water scatter the light making its path visible. The particles change the direction of the light rays.  Similarly, the tiny particles in the air scatter the blue and violet colors of the sunlight during the day.  This makes the sky appear blue. In the evenings, when the sun is near the horizon, the particles in the air scatter the red color more therefore, the evening sky appears red.

 

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