6F40.10-Blue Sky Red Sunset

6f4010blue sky red sunset-1 6f4010blue sky red sunset-2


Institute of Physics demo video

Large tank YouTube demo video

Description: This demonstration illustrates the effects of light scattering in water (similar to the atmosphere).


  • Small plastic container
  • Flashlight
  • Powdered Milk
  • Water

Setup Procedure:

  1. Fill the tank up with water.
  2. Add a little powdered milk to the water and mix it in.

Demonstration Procedure:

  1. Shine the flashlight into the water from the side.
  2. Show students the side view (see picture). Note that the beam starts out with blue reflected light and goes to a more yellowish color.
  3. Turn the tank around and have students look at the end of the light coming out. Note that it is an orange color.
  4. This shows how different colors are scattered at different lengths.
  5. When finished, turn off the flashlight.

Note: Too much powdered milk and students won’t be able to see the the beam of light on the other side.