We can thank Shannon of Victoria BC, Canada for the idea of using ordinary CDs
for the two mirrors. You can cut the CDs two ways: the proper way is with a
vice as shown by pictures sent by Shannon. She wrote, "Pictures of the
process for cutting CD's is below. Each CD makes four mirrors. Just keep bending
the CD slightly as scoring and it will cut/break clean pretty quickly."
If you forget to keep scoring as you bend, the CD will shatter and ruin the
If you don't have a vice, or if you are lazy like me, you mght be able to just cut them with a high-quality pair of scissors. When I first tried it, some of the CDs would shatter, but then yet another Canadian, Heather Dickey of Ontario, (who made the periscope project with here cub scouts) wrote in that warming the CD up first with a hairdryer eliminated the shattering problem--and it worked! And then I found that heating them in warm water works too. From this I deduce that heating many materials makes them less brittle and there must be lots of intelligent, creative women live in Canada!
Click here and print out the body pattern. Some browsers--especially Netscape--change the scale and the size of the printed pattern. If the printout says something like, "Scaled-60%" try another browser. Also, the printout has a scale check. It says 2" line to line or 5 cm line to line. Make sure it's accurate. Rough cut (bubble cut) around the solid lines and stick 4 tape "doughnuts" to the corners of the non-print side. Tape it onto the cardboard and cut out on the solid outside lines. Keep the pattern taped on until you have folded on the dashed lines in the next step.
Go here and print out the pattern for the triangle mounts. Some browsers--especially Netscape--change the scale and the size of the printed pattern. If the printout says something like, "Scaled-60%" try another browser. Also, the printout has a scale check. It says 2" line to line or 5 cm line to line. Make sure it's accurate. The illustration only shows one, but you'll need to make two. When formed into the said triangles, they will hold the mirrors in the periscope at just the right angle. Once again, rough cut them out and stick them onto cardboard using tape doughnuts. Cut out on the solid lines (next step). Don't tear off the pattern until it is folded in the next step.
Fold both the periscope body and the triangle mounts on the dashed lines. Do it with a straight edge or on the sharp edge of a desk. Kids have a hard time applying enough pressure to make the fold while at same time trying to be accurate and stay on the dashed line. For that reason, I encourage the kids to help each other out in pairs for this operation. Four hands are better than two. Also, Laurie Spurk, a teacher and Bible camp leader suggests "...if you put a ruler on the dotted lines and then trace it (pushing hard) with a pen your lines will fold easier."
When folded, the body will start look like a rectangular tube. When you're satisfied of the folding job, tear off the pattern and tape the edges together.
Similarly, fold the triangle mounts on their dashed lines and they will actually start to look like triangles. Tape one end to the other end.
The mirrors have to be taped to the hypotenuse of the triangle. This is the longer side opposite the taped ends. The triangles are right triangles (have a 90 degree angle), isosceles (have 2 sides of equal length) and they have two 45 degree angles.
Stick tape donuts to the back side of the mirror or CD, or stick it onto the hypotenuse of the triangle and attach the mirror.
On one of the other sides of triangles, stick on a tape doughnut. Push that side of the triangle into the periscope so it sticks on the inside wall. Look carefully to see how it goes in. Put a piece of on the bottom to further secure it in place. Of course, this has to be done with the other triangle on the other end as well.
Tape in both mirrors, one to each end of the periscope.
You might have to do some adjusting to get the mirrors to line up, but it's pretty intuitive.
|For explanations, activities and cool links related to light and vision click here or on the picture.|