The Scattering of Light

Purpose: To show the effects particles in the atmosphere have on light

Materials

• large glass
• whole milk
• teaspoon
• flashlight
• 8 1/2" x 11" piece of cardboard
• hole puncher
• pencil
• science journal

Procedure

1. Fill a large glass full with water and let it sit for 15 minutes until any particles in the water have settled to the bottom.
2. Using a pencil or a hole puncher, punch a small hole in the center of a piece of cardboard.
3. Hold the piece of cardboard in front of a flashlight beam, so that the flashlight is touching the cardboard and a thin beam of light is visible through the hole.
4. Turn off the lights in the room and aim the flashlight towards the glass.
5. Observe what happens to the light as it travels through the glass and note the shape of the beam. Record your observations in the science journal.
6. Add a teaspoon of milk to the glass of water and repeat steps 3-5.
7. Continue to add milk to the glass of water one teaspoon at a time. Repeat steps 3-5 and observe and record after each teaspoon.
8. Continue until the glass appears to be more milk than water.

Conclusion

1. What observations can be made about the light beam as it goes through the glass of water?
2. Did the color of the contents inside the glass appear to change? If so, describe how it changed and explain why?
3. As the milk was added to the glass of water, what happened to the path the light beam traveled? Why?
4. If the water represents the air in the atmosphere, and the milk represents the particles (aerosols) in the atmosphere, what connections can be made?

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Answer Key

1. What observations can be made about the light beam as it goes through the glass of water?

The light bends (refracts) as it enters a different medium.

2. Did the color of the contents inside the glass appear to change? If so, describe how it changed and explain why?

The color of the contents inside the glass appeared to become whiter due to the increase of milk.

3. As the milk was added to the glass of water, what happened to the path the light beam traveled? Why?

As the milk was added to the glass of water, the light beam scattered (refracted and reflected) in all directions off the tiny milk particles. The fat particles in the milk scattered the light, causing the water to appear redder since most of the blue light waves scattered out.

4. If the water represents the air in the atmosphere, and the milk represents the particles (aerosols) in the atmosphere, what connections can be made?

The aerosols in the atmosphere scatter the light. As the number of aerosols increase in the air, the light scatters (reflects and refracts) more.