How to make a periscope
Look around corners and over walls with this awesome periscope you can make at home
1. Create the tube
The first thing you will need to do is create a tube in which your mirrors will fit. Take two rectangular juice cartons and carefully cut the angled tops off them both with scissors. Cut four two-centimetre-long strips at the end of one carton, then slot the two cartons together with two of the flaps inside the other carton and two outside. Attach the two cartons together tightly with tape.
2. Cut the slots
Now you need to create slots for the mirrors. On the side of the carton at each end mark a 45-degree line. Make sure both lines are at the same angle, then turn over the carton and draw the same on the other side. You need to ensure that the lines are facing each other on both sides of the carton so the mirrors will slot in when you need them to.
3. Add the mirrors
Cut out two eight-centimetre-square sections of thick card, then glue a six-centimetre mirror to the centre of each of these squares. While they dry, use your scissors to cut slots where you marked the 45-degree lines on the carton a moment ago. The mirrors stick out a little on the card, so you may need to cut a little extra out of the slit to make them fit properly.
4. Viewing holes
Once the mirrors are in, you can secure them in place with tape. Next, you’ll need to cut out two holes in the box – one for your eye to look through and one so you can see the outside world. Draw around a bottle top and cut out the hole for your eyehole, then cut out a rectangle around five centimetres across and four centimetres high at the other end so you can see out of it.
5. Try it then tweak it
When you hold the eyehole up to your eye, you should be able to see through the hole at the other end of the periscope. Try looking over and around objects, over crowds or through doorways. You can also try making another periscope with one of the mirrors angled in a different direction if you want to see what’s going on behind you.
When light hits the mirror, it is reflected straight down the tube of your periscope because the angle of the mirror is 45 degrees. The second mirror then reflects the same light into your eye. The angle is really important, so if you can’t see out of your periscope you might need to check it’s definitely aligned at exactly 45 degrees.
This article was originally published in How It Works issue 122
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