Light Mixing

The goal of the series of experiments is to allow students to learn how different colors of light can interact and mix to produce various new colors. The experiment utilizes 3 different color LEDs (red, green, and blue) to produce a wide range of colors. Many of the current video displays, such as a computer monitor or TV, uses the concept of additive color, where three different colors of light are combined in order to produce a wide range of colors. The primary colors often used are red, green, and blue. Through different combinations and proportions, it is possible to cover the entire visible spectrum. For example, equal parts of red and green, green and blue, and red and blue produce yellow, cyan, and magenta, respectively. These generated colors are known as additive secondary colors. Combining all three primary colors creates white light.


  • Red LED (brighter the better)
  • Blue LED (brighter the better)
  • Green LED (brighter the better)
  • 9V battery (x3)
  • Resistor 470 W (x3)
  • Switch (x3)


  1. Shine LEDs on white wall or white paper.
  2. Try different combinations of LEDs to produce the three secondary colors.
  3. Combine all three and see what color is created.
  4. Change the amount of illumination of each of the LEDs by varying the distance to see if other colors can be created. For example, red and green in equal parts produce yellow. What is necessary in order to produce orange?


A potentiometer can be added into the circuit in order to control the amount of current fed into the LED. This can be an alternative means of controlling the light intensity instead of changing the distance to the white wall/paper.