The picture on a television screen is made up of thin lines of light. In the first project, you will see that a television picture is made up from rows of glowing dots of colored light. The picture consists of just three colors – red, green, and blue. Viewed from a distance, these colors mix to produce the full range of colors that we see naturally around us – as the second experiment demonstrates.
Fax machines work in a similar way to television, only more slowly. When you feed a sheet of paper into a fax machine, a beam of light moves back and forth across it. Dark places absorb the light, and pale places reflect it. The reflected light enters a detector that produces an electric current. The electric current is changed into a code made up of chirping sounds. These travel down the line to the receiving fax machine. This code controls a scanner that moves across heat-sensitive paper and produces a facsimile of the original. The final project shows how a fax machine breaks an image into tiny squares that are black and white.
YOU WILL NEED
- TV screen:
TV set, flashlight, powerful magnifying glass.
- Secondary colors:
Red, green, and blue transparent plastic sheet, 3 powerful flashlights, 3 rubber bands, black card.
- Digital images:
Ruler, pencil, tracing paper, photograph, black felt-tipped pen.
Turn off the TV. Shine the flashlight close to the screen and look through the magnifying glass. You will see that the screen is covered in very fine lines.
Turn on the TV and view the screen though the lens. The picture is made up of minute rectangles of light colored red, green, and blue.
Attach a piece of colored plastic over the end of each of your three flashlights. Stretch the plastic tightly, and use a rubber band to hold it firmly in place.
Shine the flashlights onto the black card. You can see the three different primary colors of red, green, and blue.
Position the flashlights so that the three circles of colored light overlap in a clover leaf pattern. Overlapping colors mix to give new, secondary colors.
Draw a line ¼in apart to cover the tracing paper over the photograph. Use the pen to fill each dark square. Leave each light square blank.
The result is a "digitized" image, which means it can be represented by numbers-the digit 1 for the white squares, and the digit 0 for black squares. The digitized image contains less detail than the original ph+oto. One could increase the details of the image by using a greater number of smaller squares.
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