ADDITIVE AND SUBTRACTIVE COLORS

Introduction

As you know, white light is a combination of many colors. The objects you see around you obtain their colors from light. The objects absorb some wavelengths and reflect others. Your eyes register the wavelengths that are reflected. A book with a red cover, for example, is reflecting the wavelengths your eyes interpret as red and absorbing all the others.

In technology, colors are produced using two processes, the additive process or the subtractive process. Each process is used for different purposes.

With the additive process, the color comes from light waves emitted directly from a particular source. Red, green, and blue wavelengths of light are added together in differing amounts and in various combinations to produce all other colors. They are referred to as the additive primary colors. The colors produced by a television picture tube are created in this way.

With the subtractive process, coloring agents, such as ink or paint, are used. The ink or paint absorbs certain wavelengths of light and reflects others. Cyan, magenta, and yellow are the subtractive primary colors. When combined in different ways, they can also produce all other colors. They are the same colors used in four-color process printing.

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Your Task

For this WebQuest, your job is to learn more about how colors are produced. To demonstrate what you have learned, you will answer the questions included here. You will also complete one of the activities described at the end of this WebQuest.

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Process

Read through the following questions. Then research the Internet resources that are provided for you.. As you explore the sites, look for answers to the questions. Keep a record of any sites where you find answers by noting the title and URL (Internet address). For example:

            (title) Technology Student Association
            (URL) www.tsaweb.org

1. The additive primary colors are commonly referred to by which three initials?
   
   
2. You probably learned in school that the primary colors are red, yellow, and blue. Why aren’t these the same primary colors used for printing?
   
   
3. What happens when you combine all three additive primary colors?
   
   
4. Which process is occurring when our eyes perceive colors in everyday objects, additive or subtractive?
   
   
5. What is chromatography used for?
   
   
6. Who first proposed the theory that white light was a combination of many colors?
   
   
7. When was color first reproduced in a printed book?
   
   

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Internet Resources

Visit the Web sites listed here to find information that will enable you to answer the questions. You may use additional sites if you wish. Be sure to keep a record of any sites you use.

• Understanding Color explains both the additive and subtractive processes.
  
  
• Color Subtraction is an interactive site that allows you to make your own color combinations.
  
  
• Black Magic is an activity in which colors are separated out of the ink in a black marking pen.
  
  
• About: Inventors—The History of Printing and Printing Processes provides an overview of printing.
  
  
• Newton, Sir Isaac discusses his contributions to the science of optics.
  
  

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Activities

Several activities are described below. Complete one of these activities (your choice) to demonstrate the understandings you’ve gained by going on this WebQuest.

• Using three flashlights and transparencies in different colors, conduct experiments to produce different colors.
  
  
• Create a poster explaining the additive and/or subtractive color process.
  
  
• Take part in a panel discussion about the many ways in which printing has changed our lives.
  
  

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