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Mirrors and Images

What is it that lets us see objects? Some objects, such as the sun, give off their own their own light. Most objects, however, do not. These objects must reflect light in order to be seen. For instance, the walls in the room do not put out their own light; they simply reflect light from overhead lights or from sunlight that enters the room through a window. Smooth, polished surfaces, like mirrors, are very good at reflecting light.

When you place an object between two hinged mirrors, light from the object bounces back and forth between the mirrors before it reaches your eyes. An image is formed each time the light bounces off a mirror. The angle between the two hinged mirrors has a special relationship with the number of images you see. Try to find out what it is!

Required Materials

  • Science notebook
  • A pencil or some other object, such as a coin or paper clip
  • 2 4 x 6-inch mirrors
  • Masking tape
  • Paper
  • Protractor

Activity Directions

  1. Work with a partner. Take two mirrors and place them together with the shiny sides facing one another. Tape them along the side to form a hinged door. The mirrors should be able to open freely like a book.

  2. Take a piece of paper or cardboard. Using a protractor, measure and mark angles (by drawing a line) of 180 degrees, 90 degrees, 60 degrees, 45 degrees, 36 degrees, 30 degrees, and 20 degrees.

  3. Place the hinged mirrors at each of these angles and put an object (it could be a coin, a pencil, an eraser, or some other item you may have at your desk) between them as close to the mirrors as possible.

  4. Count the number of images you see and record your observations in your science notebook.

  5. When you are finished, answer the following questions in your science notebook:

      What happened to the number of images you saw as you changed the angle from 60 to 45 degrees between the mirrors?

      What happened to the number of images you saw as you changed the angle from 30 degrees to 60 degrees?

      Can you now make a statement about how the angle between the mirrors determines how many images will be produced?

      Compare your findings with the findings of other groups. Is the information the same?

      If not, then what do you think might be the reason for them being different?

      If you were to do this experiment again, what would you change and why?

Interactive Java Tutorial
Multiple Images
Explore how two hinged mirrors can produce multiple images. 

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