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Reprinted by permission of Dick Berg, University of Maryland, for use on this website.

The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources.

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Put the pinhole slide into the slide projector and then set the projector so that it points into the tank at an angle. The mirror in the tank is also set at an angle so that a round oval of light is projected onto the ceiling. Due to the index of refraction between the air and the water one of the rims of the oval is red and the other is blue or violet. Now if you add a few drops of milk or coffee creamer, the milk particles add scattering and as the shorter wavelengths are scattered most the rims start to change colors. If the right amount of milk is added the blue rim goes from violet to green. 

The above experiment can also be used to show forward and back scattering. Add the milk or coffee creamer to the water. Instead of using the projector, shine a laser through the tank. If you look at the tank from the laser position or the side you will see some back scattering. If you look at the beam from in front of the laser you will see that the forward scattering is much more intense than the back scattering.