All the Colors of Light
Another important thing that Newton did was to figure out a lot about how light works.
One day he bought a prism at the Stourbridge Fair. (This is a piece of glass shaped
like a triangle.) He had it sitting on his desk, and noticed how when the sun shone on it,
he got different colors out. This made him very curious. Does this change the light, or
does the sunlight have lots of colors that the prism puts into different places? How does
the prism do it?
To find the answers, Newton had to do some experiments. He first used his blinds to get
a very thin sunbeam to hit the prism. This was important - to control the light that was
coming in so that he knew exactly what he was starting with. He discovered that the
separation of light was even clearer. There was red, then orange, then yellow, then green,
and then blue.
Newton was pretty sure that what was happening was that the light from the sun had
all these colors in it, and that what the prism was doing was bending them all to go into
slightly different directions. To test this he got two prisms and a card with a hole in it.
He used the first prism to get the sunlight to make different colors. Then he would choose
a color and put the hole so than only that color went through into the next prism. He
then had a very thin line of red, yellow or some other color of light going to the second
prism.
He discovered that when the light came out of the other side of the next prism, it was still
the same color as when it went in. So the prism doesn't change the light's color. What the
prism did do was to bend the path the light went on, so that it hit a different place than
when the prism wasn't there. When he tried different colors of light he found that the prism
bent them all a little bit differently. That was why light that looked white, which had all
the colors in it, made different colors when it went through the prism - the different colors
all came out of it in slightly different directions.