• Flashlight

• Sheet of white paper

• Clear glass or plastic bottle

• Water (enough to fill ¾ of a bottle)

• Milk or cream (1–3 tablespoons)

1. Fill the bottle ¾ full with water.
2. Turn on the flashlight and darken the room.
3. Shine the flashlight through the side of the bottle.
4. Look through the side of the bottle. What do you see?
5. Look through the bottle straight at the light. What do you see?
6. Hold the paper opposite the light. What color is on the paper?
7. Add 1 tablespoon of milk to the water.
8. As the milk mixes with the water, repeat steps 4–6.
9. If you don’t see a change, alternate watching the milky water with the flashlight on and off.
10. Do you see a light blue hue through the side of the bottle? Does the light move through the entire bottle the same way? Has the reflection on the paper changed colors? As the milk sinks, is the light going through the top and bottom of the bottle differently?

Want to Learn More? Read an article related to this activity:

• The Reflection of Light

• The Refraction of Light

To find this experiment and many more please download the Lighten Up! Discovering the Science of Light book, developed through a partnership with the Optical Society of America’s Foundation (OSAF) and the Girl Scouts of the USA.