In this science experiment we will make a pinhole projector to view an eclipse. If you decide to view an eclipse, the
first thing you must know is this, never view the sun with the naked eye or with any optical device, such as binoculars
or a telescope!
This is more than advice. Why? As a kid, did you ever take a magnifying glass out into the sun and burn leaves? If so,
you probably remember that when the focused sunlight coming through the lens was refracted and concentrated to a
small spot, the energy available there was truly remarkable. Guess what? You have a lens just like that in your eye. If
you look at the sun, your eye-lens will concentrate the sun's light and focus it to a very small spot on the back of your
retina. This can cause permanent eye damage or blindness. Additionally, there are no pain sensors back there so
you won't even know it's happening! Have I scared the willies out of you? Good!
There are safe ways to view the sun. The simplest requires only a long box (at least 6 feet long), a piece of aluminum
foil, a pin, and a sheet of white paper.
The length of the box is important. The longer the box, the bigger the pinhole image. To find the size of the image,
multiply the length of the box by the number 0.00873. For a box that is 1 meter long, the image will be 0.00873 meters
(or 8.77 mm) in diameter. If your box is 5 feet (60 inches) long, your solar image will be 60 x 0.00873 = 0.52 inches in
diameter. If you want to round things off, the size of the image is about 1/100th the length of the box.
If you can't find a long box or tube, you can tape together two or more boxes to make a longer one. In the illustrations
below, we found that taping together two triangular UPS shipping tubes works well. Of course, if you do this, you
must cut out the cardboard at the ends of the tube in the middle!
Process To Make A Pinhole Projector To View Eclipse
1) Find or make a long box or tube
If you can't find a long box or tube, you can tape together two or more boxes to make a longer one.
We found that taping together two triangular UPS shipping tubes works well. Cut out the
cardboard at the ends of the tube and tape them together with duct tape in the middle.
2) Cut a hole in the center of one end of the box.
3) Tape a piece of foil over the hole.
4) Poke a small hole in the foil with a pin.
5) Cut a viewing hole in the side of the box.
Cut a viewing hole in the side of the box near the paper, then put a piece of white paper inside
the end of the box near the viewing portal.
Point the end of the box with the pinhole at the sun so that you see a round image on the
paper at the other end. If you are having trouble pointing, look at the shadow of the box on the
ground. Move the box so that the shadow looks like the end of the box (so the sides are not
casting a shadow). The round spot of light you see on the paper is a pinhole image of the sun.
Do not look through the pinhole at the sun! Look only at the image on the paper.
Now grab some friends and make a pinhole projector to view the next eclipse!
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