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What White Light Is
White light is a mixture of all the rainbow's colors, and a prism splits it because each color bends by a slightly different amount.
4 steps, drawn by Nib. Read it here, or watch him draw it. Updated .
1white is a bundle
Sunlight looks colorless, or plain white. But it is not one thing. It is many colors of light traveling together, all at once, in the same beam. Our eyes add them up and report 'white'.
Sunlight looks plain, but it is a bundle of many colors traveling together.
a common mix-upWhite light is its own pure, simple kind of light with no colors inside it.
2light vs paint
The word 'mixing' here means colored lights adding together, like several flashlights with colored filters shining on the same wall spot. Red, green, and blue lights overlapping make white. This is different from mixing paint, where each pigment soaks up some light and the blend turns muddy. Light mixing adds; paint mixing subtracts.
Colored lights add up to white; paint mixing is a different process and does not.
a common mix-upMaking white light is like mixing paints; it is really colored lights adding up.
If you shine red, green, and blue flashlights on one spot of a wall, what color do you see where they overlap?
Show the answer
White, because the lights add together.
3the prism
You can undo the mixing. A glass prism bends light as it enters and again as it leaves. Each color bends by a slightly different amount: violet the most, red the least. Because the bends differ, the colors that traveled together leave on separate paths and spread into a fan.
A prism bends each color by a slightly different amount, so the bundle fans out.
Which color bends the most in a prism, and which the least?
Show the answer
Violet bends the most and red the least.
4the rainbow order
That fan of colors is the same order you see in a rainbow: red, orange, yellow, green, blue, violet. A rainbow is raindrops doing a prism's job. The colors were never made by the glass or the water. They were hidden in the sunlight all along, and bending simply sorted them.
A rainbow is the colors hidden in sunlight, sorted apart.
a common mix-upThe prism or raindrops create the colors.
So sunlight is a team of colors, not one color. Next, we'll see what happens when that team runs into air, because air treats each color differently.