When mixing colors of light, why does combining a secondary color with its complementary color give white light?

I can't find the answer in my book, please help!

unit 5 lesson 4 color (connexus)

1) red and yellow
2) complementary
3) complementary
4) split complementary
5) anger and war

well, if you buy into the fact that

red+green+blue = white
then the complement of any secondary color is the unused primary color.

When mixing colors of light, the phenomenon of combining a secondary color with its complementary color and producing white light is known as color addition or additive color mixing.

To understand why combining a secondary color with its complementary color gives white light, we need to explore the concept of color perception and the behavior of light.

In color perception, we have three primary colors of light: red, green, and blue. All the colors we see are created by mixing varying intensities of these primary colors. When two primary colors are mixed at full intensity, they create a secondary color. The secondary colors are:
- Mixing red and green light produces yellow light.
- Mixing red and blue light produces magenta light.
- Mixing green and blue light produces cyan light.

Now, let's consider adding the complementary colors:
- The complementary color of yellow is a combination of red and blue, which is magenta.
- The complementary color of magenta is a combination of red and green, which is yellow.
- The complementary color of cyan is a combination of blue and red, which is magenta.

When we mix a secondary color with its complementary color, the combined light contains all three primary colors (red, green, and blue) in varying intensities. This combination effectively stimulates all the cone cells in our eyes responsible for color vision, which perceive red, green, and blue light.

Since our eyes perceive all three primary colors simultaneously in equal proportion, our brain interprets this equal stimulation of cone cells as white light.

Hence, when we mix a secondary color with its complementary color in the context of color addition, we perceive white light because all three primary colors are present in equal intensity.

In summary, combining a secondary color with its complementary color produces white light because their mixture stimulates our eyes' cone cells equally, resulting in the perception of all three primary colors simultaneously and thus white light.