Colored shadows

Two shadows can be seen on the wall, one of which appears green and one red. Where the shadows overlap, it is darkerThe red shadow is the shadow that belongs to the green lamp. The green shadow is the shadow of the red lamp (see lamp position above).

A white wall is illuminated with the two lamps. The wall appears yellowish white in the combined light. Now place an object between the lamps and the wall.

• a red and green headlight or two bulbs (preferably not frosted glass) covered with red and green headlight film,

• Incandescent lamps with frosted glass bulbs cast a blurred shadow.
• Some light bulbs have a longer filament. Depending on the orientation of the light filament in relation to the wall, the edges of the shadow will vary in sharpness. If you turn the lamp, you can optimize the sharpness of the shadow.
• Make sure the surroundings are as dark as possible. The effect will then be all the clearer.

What is technically behind the experiment

This experiment makes it very clear that shadow is to be understood as the absence of light. Red and green light appear together as yellowish white light. If there is no red light, the shadow appears green. And vice versa, if green light is absent, the shadow image appears red. The green shadows are areas where green light falls, but no red light. Where neither red nor green light falls, the wall appears dark.

What the experiment has to do with everyday life

The fact that several shadows are created that overlap can also often be observed in everyday life. Think, for example, of the shadows of soccer players under floodlights. Here, too, the shadows are areas where the light from one spotlight is missing.

Rita Wodzinski