Mixing Colors

There are three primary colors of light are red, green, and blue.  The three primary colors of paint are red, yellow, and blue (I know it's actually cyan, yellow, and magenta, which we'll get to in more detail later, but for now just stick with me and think of the primary colors of paint as red-yellow-blue and I promise it will all make sense in the end).

Most kids understand how yellow paint and blue paint make green paint, but are totally stumped when red light and green light mix to make yellow light. The difference is that we're mixing light, not paint.

Lots of science textbooks still have this experiment listed under how to mix light: "Stir together one of red water and one glass of green water (dyed with food coloring) to get a glass of yellow water." Hmmm... the result I get is a yucky greenish-brown color. What happened?

The reason  you can't mix green and red water to get yellow is that you’re essentially still mixing paint, not light. But don’t take our word for it – test it out for yourself with this super-fast light experiment on mixing colors.

Materials:

• pair of scissors


• crayons


• sharp wood pencil or wood skewer


• index cards


• drill (optional)

[am4show have='p8;p9;p11;p38;p92;p19;p46;p66;p89;' guest_error='Guest error message' user_error='User error message' ]



Download Student Worksheet & Exercises

Here's what you do: use a cup to outline circles on a sheet of stiff white paper (or manila folders). Stack several blank pages together and cut out multiple circles. Color the circles, push a sharp wooden pencil through a hole in the center, and spin! What color does yellow and blue make? Pink and purple? You can also make a button-spinner to really whirl it around by looping a length of string through two holes in the center of the disk circle.

Troubleshooting: These disks needs to spin rapidly in order to trick your eye into blending the colors. If you have a motor, batteries, and wires lying around, you can use them to spin the disks for you. Simply punch the motor’s shaft through the paper (colored-side up).

Turn the motor on by connecting the power and watch the colors mix! Other alternatives include using a drill, hand-held mixer/beaters (not a Kitchen Aid standard mixer!), electric screwdriver, etc.

Alternate Spinning Method: Want to do this project, but you don't have enough speed or a motor?  You can make a 'button spinner' to whirl these things around super-fast.  (Did you know this is how the first circular saws were made?)

Attach your disk to a piece of stiff cardboard (index cards are too flimsy), punch out two holes near the center and thread a loop of string through and tie the ends together to make the old-fashioned “spinning disk”. Using a circling motion with your hands, you can twist up the string with the card in the middle and then pull horizontally outwards to untwist it and watch the cardboard whirl and whip around!!

Click here for the Mixing Cold Light experiment!

Exercises

1.  What happens when blue and red are mixed on the spinner?


2.  What happens when red and green are mixed on the spinner?


3. What colors would you mix to get orange?


4. What are the primary colors of light, and how do they differ from the primary colors we learn in art class?

[/am4show]