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  • Visitors interact with the Colored Shadows exhibit.
  • Visitors interact with the Colored Shadows exhibit.
  • An additive mixture of light makes for some colorful fun.

  • Visitors interact with the Colored Shadows exhibit.
  • Visitors interact with the Colored Shadows exhibit.
  • Colored Shadows Demo

Colored Shadows

Not all shadows are black.

Step in front of this wall, and you’ll make shadows of various colors—yellow, magenta, cyan, red, green, blue, and yes, even black—that wiggle, jump, and dance along with you.


Where:   Bechtel Gallery 3: Seeing & Reflections
Exhibit Developers:   Exploratorium Founder Frank Oppenheimer and Richard O. Brown, 1975

What’s going on?

When lights of different colors shine on the same spot on a white surface, the light reflecting from that spot to your eyes is called an additive mixture because it is the sum of all the light. 

At this exhibit, a red light, a blue light, and a green light are all shining on the screen. The screen looks white because these three colored lights stimulate the three types of cones in your eyes approximately equally, creating the sensation of white. We call this set of three colors—red, green, and blue—the additive primaries of light.

With these three lights you can make shadows of seven different colors—blue, red, green, black, cyan, magenta, and yellow—by blocking different combinations of lights: When you block two lights, you see a shadow of the third color—for example, block the red and green lights and you get a blue shadow. If you block only one of the lights, you get a shadow whose color is a mixture of the other two. Block the red light and the blue and green light mix to create cyan; block the green light and the red and blue light make magenta; block the blue light and red and green make yellow. If you block all three lights, you get a black shadow.

It may seem strange that a red light and a green light mix to make yellow light on a white screen. It just so happens that a particular mixture of red and green light stimulates the cones in your eyes exactly as much as they’re stimulated by yellow light—that is, by light from the yellow portion of the rainbow—so your eye can't tell the difference.

Diagram showing paths of light in the Colored Shadows exhibit. As you move in front of the wall, your body can block one, two, or all three of the lights, resulting in shadows of various colors. (click diagram to enlarge)

 
Phenomena: Color, Color: Complimentary, Color Mixing, Shadows
Keywords: CMY, RGB
Aliases: Color Splitter, Wall Watching Bench
Collections: Colorfest, Seeing the Light, Young Kids

More to explore

Colored Shadows Demo

An additive mixture of light makes for some colorful fun.

Science activity that demonstrates perception of additive color mixtures
Colored Shadows

Not all shadows are black.

Truly Primary Pigments

Watch colors play in this quick exploration of layering hues.

Self-Portrait Silhouettes
Self-Portrait Silhouettes

Make a photographic image without a camera!

Related exhibits

Pixel Table
Pixel Table

Create myriad colored shadows with mirrored tubes.

Sun Painting
Sun Painting

Sunlight–reflected and refracted–paints an ever-changing color composition.

Aurora
Aurora

A reflector stretches light from colored tiles into long bright ribbons.

Sophisticated Shadows
Sophisticated Shadows

Explore images made from shadows.


IMLS acknowledgment

This web project was made possible in part by the Institute of Museum and Library Services [MA-30-16-0175-16].

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