Perception of

This demonstration in the show is designed to provide some insight into how we perceive colors. We use a laser pointer to show something about color. Laser pointers are usually red. When you point it at a white card you can see the red dot of the pointer. When we shine it through a clear solution in a beaker the red dot is still there on the card.

Then we take a solution of red food coloring in water. Many people expect this red solution to absorb the red light from the laser pointer. When we do the experiment, however, the red dot still shows up on the card. The reason for this observation is that a red solution is NOT absorbing the red frequencies of light. We perceive the solution as red precisely because the red light is escaping the solution and reaching our eyes. Therefore, the red solution doesn't absorb the red light of the pointer.