Exploring the Science of Light
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Watch TV Upside Down on a Piece of Paper

Required Materials

  • A magnifying glass

  • A piece of white paper

  • A television

Activity Directions

You can make an image with your magnifying glass of almost anything: a window with the sun shining through it, a tree outside in your yard, or even the dog in your neighbor’s yard. However, these are rather boring things to look at, especially when your home contains something much more entertaining. One of the greatest image-generating sources in your house is the television set.

  1. Turn off the lights, tune your TV to your favorite show, and stand back about ten feet from the set.
  2. Hold the lens in one hand and the paper in the other.
  3. Position the lens vertically between the TV and the paper and hold the paper about six inches from the lens.
  4. Both the lens and the paper should be parallel to the TV screen and at right angles to the floor.
  5. Move the paper away from and toward the lens until you see a focused image of your television picture.
  6. Sit back and watch the show-but you may have to turn your head upside down, because the image is inverted and backward.
If you are not satisfied with the size of your image, you can change the magnification by changing your distance from the TV set. Try standing twenty feet from the set and then try two feet.

Here’s What’s Happening

When light leaves a point on the TV, it spreads out it many different directions. As a result, light from one point on the TV hits the entire surface of the magnifying lens. The lens then bends and redirects this light so that it comes back together again as a single point. This happens to every point of light that makes up the image on the TV screen. In this way, the TV image is reconstructed by the lens.

The lens bends light from the left portion of the TV, redirecting it to the right portion of the image, and the right portion to the left. Light from the top of the TV gets redirected to the bottom of the image and vice versa. As a result, the image is upside down and backward.

You may notice that when you are closer to the TV, you have to hold the paper farther from the lens to find a clear image than when you are farther away from the TV. The location of the focal point of a lens determines the size of the image and the distance of the image from the lens for any particular distance to the object.

Want to Learn More? Read an article related to this activity:

To find this experiment and many more please read Light Action! Amazing Experiments with Optics by Vicki Cobb and Josh Cobb, illustrated by Theo Cobb. To purchase a copy click here.

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