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Science_Lab_Yellow / Lesson 1: Color From White Light

Color From White Light

What will we be learning today?

  • In this lesson, we are going to learn how you get color from white light.

  • How Do You Get Color from White Light?

    When Sir Isaac Newton passed a beam of white sunlight through a prism-a triangular piece of cut and polished glass-in a dark room, he was startled to see a band of rainbow colors. He called the color band a spectrum after a word meaning "ghostly vision."


    Newton wanted to know more about the colors cast by the prism. Where did they come from? He believed that white sunlight was actually a mixture of all the colors. The prism simply spread the colors out by refracting each one at a different angle. Red is refracted the least, violet the most.


    Later, Newton predicted that if the spectral colors cast by one prism were passed through a second prism, the colors would recombine into white light.


    The result proved his prediction was right. White light is really made up of many colors, including red, orange, yellow, green, blue, and violet.




    Rainbow

    The rainbow colors you see after a storm result from water drops that act both as prisms and mirrors. The drops bend rays of sunlight at different angles, causing the colors to spread out. Then the various colors reflect off the back of the drops into your eye. As the drawing shows, that is how rainbows form in the sky.


    Can you make a rainbow with a garden hose? If you've stood with your back to the Sun and looked at the fine mist from a hose, fountain, or waterfall, you've probably seen a rainbow form.




    You can also make a rainbow indoors, as this student is doing. Fill a clear-plastic cup about halfway with water. Carefully place it on the edge of a table. A third of it should extend over the edge. Hold a piece of white paper directly behind the cup. Shine a flashlight vertically through the bottom of the cup. You should see a rainbow on the paper.



    You can also make a rainbow indoors, as this student is doing. Fill a clear-plastic cup about halfway with water. Carefully place it on the edge of a table. A third of it should extend over the edge. Hold a piece of white paper directly behind the cup. Shine a flashlight vertically through the bottom of the cup. You should see a rainbow on the paper.


    When the spinner is twirled at the right speed, you can see all the colors turn into white.


    What colors would you put on your spinner to try to produce white light?