Color Mixing and Shadows

Using red, green, and blue light sources aimed at a shadow screen, students explore how shadows change color and how overlapping beams of light combine to create new colors. The activity demonstrates that the primary colors of light (red, green, and blue) mix differently than paint pigments.

1. Set up a white wall or screen in a darkened room.
2. Arrange three light sources (such as colored LED bulbs or flashlights covered with red, green, and blue filters) so they shine on the screen from slightly different angles.
3. Place an object (such as a marker or hand) in front of the lights to cast shadows.
4. Move the object closer to and farther from the wall to observe how the shadows become sharper or blurrier.
5. Observe that multiple shadows appear in different colors depending on which light beams are blocked.
6. Unscrew or turn off one colored light at a time to see how removing a color changes the resulting shadows and glow.
7. Experiment with colored objects (such as a yellow bag or multicolored logo) to observe how their appearance changes under different light combinations.

Colored light shadows color mixing…great student activity - Homemade Science with Bruce Yeany:

Colour Mixing with Light Experiment | Kids Science - Explore Planet English:

📄 Color Mixing Shadows - Inventors of Tomorrow: https://inventorsoftomorrow.com/2018/07/23/color-mixing-shadows/

• Use 3 video projects with a different color projected each as powerful light sources.
• Use remote-controlled dimmers or switches so students can safely control light intensity.
• Place lights behind a translucent screen or box to reduce glare and increase safety.
• Try mixing just two colors at a time (red + blue, red + green, green + blue) and compare results.
• Replace bulbs with programmable RGB LEDs for more precise mixing.

• Do not stare directly into bright LED bulbs; diffuse light with a translucent screen if possible.
• Prevent children from touching or unscrewing bulbs; assign adults to handle equipment.
• Secure light fixtures to prevent tipping or breakage.
• Cover unused power strip outlets with outlet covers.

• Why do we see multiple shadows in different colors? (Each shadow blocks one or more of the light sources, leaving the other colors to show.)
• How is mixing colors of light different from mixing paint? (Light uses additive mixing—red, green, and blue make white light—whereas paint uses subtractive mixing.)
• What happens to a colored object under different light sources? (It only reflects certain wavelengths, so its apparent color changes with the light available.)
• Why do shadows appear sharper or blurrier depending on distance from the screen? (Closer objects block light more directly, producing sharper shadows; farther objects allow overlapping edges.)