How to Make a Periscope

A periscope allows you to look over at objects or people from around a corner, or from a higher vantage point than normal. While modern submarines and other high-tech vehicles usually use a more complex system of prisms and lenses, the basic mirror periscope described below is easy to make at home, and provides a clear enough image that it was widely used for military purposes well into the twentieth century.^{[1]XResearch source}

Method 1

Method 1 of 2:

Making a Cardboard Periscope

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1
Find two small mirrors the same size. You can use any flat mirrors, whether the frame is rectangular, round, or some other shape. The two mirrors don't even have to be the same shape, but they do need to be small enough to fit into a milk carton.^{[2]XResearch source}
- You may be able to find small mirrors at a craft or art supply store, or from an online store.
2
Cut the tops off two clean milk cartons. Find two empty milk cartons, each at least one quart (one liter) in size and wide enough to fit your mirrors. Cut off and discard the triangular top of each one, then wash the inside thoroughly to get rid of smells.^{[3]XResearch source}
- A long, sturdy cardboard tube could also work.
- You could use a large, flat sheet of sturdy cardboard instead. Lightly score it with a craft knife to divide it into four sections, then fold it into a box and tape together.
- You can use two sturdy paper boxes.
- Or stick several layers of recycled toilet paper together to make a sturdy base.
- You can even use shipping paper.
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3
Tape the two cartons together. Use packing tape or another strong tape to tape the open ends of the cartons together, making one long box. To fasten the cartons together more securely, try taping the inside of the box together on one side, then taping all four outside surfaces.
- You can tape two tubes or two homemade cardboard cartons together in the same way, to make a longer periscope. However, the longer the periscope is, the smaller the image will be.
4
Cut a hole on one side just big enough for a mirror. Place one of the mirrors on one of the vertical sides of the milk carton, about 1/4 of an inch (6 mm) from the end.^{[4]XResearch source} Trace the mirror with a pencil, then cut on the pencil marks to create a hole.
- A craft knife may be the easiest tool for cutting the hole, but should only be used with adult supervision, as it is very sharp.
- If you are using a cardboard tube instead of a milk carton, flatten it slightly so you can trace the mirror.
5
Insert a mirror facing the hole at a 45º angle. Use sticky putty or double-sided tape to attach the mirror you traced onto the inside wall of the carton, across from the hole you cut. Arrange the mirror so the whole surface can be seen when you look through the hole, but have it point downward toward the opposite end of the carton at a 45º angle.^{[5]XResearch source}
- To test whether it's at a 45º angle, use a ruler to measure the distance from the closest corner of the carton to where the lower edge of the mirror touches the carton's side. Then measure the distance from the same corner to the opposite end of the mirror, where it touches the carton's top. The two distances will be the same if the mirror is angled at 45º.
- Don't use glue yet, since you might need to make adjustments to the mirror's position.
To find out where to cut, place the carton in front of you on its short end, with the first hole you cut near the top. Rotate the carton so that hole is on the opposite side. The second hole will go on the side that is now facing you, right at the bottom of this side. Trace the second mirror and cut as you did before.^{[6]XResearch source}
Just like the first mirror, this should be visible from the hole, and should face the other end of the carton at a 45º angle. At this angle, one mirror will reflect light directly down through the periscope, and the second will reflect it directly through the hole and into your eye. You will see this reflected light as an image of whatever is on the opposite hole of your periscope.
Do you see a clear image when you look through one of the holes? If it is blurry, or you only see the inside of the periscope, adjust the position of the mirrors. Once both of them are at 45º angles, you should be able to see through the periscope clearly.^{[7]XResearch source}
9
Attach the mirrors permanently. If putty or tape isn't enough to keep the mirrors steady, attach them with glue. Once they're permanently stuck in the right position, you can use your periscope to spy on people, or see over the top of a crowd.
- If too much light is coming through the "eye" end of your periscope, making it difficult to see the reflection, tape black construction paper over the outside edges of the hole.

Method 2

Method 2 of 2:

Making a Periscope from PVC Pipe

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Find one or two pieces of PVC pipe. Try to find a piece somewhere between 12" and 20", but be aware that the longer the pipe is, the smaller the image will be. You may also use two sections of slightly different sizes, so one fits snugly into the other. This lets you rotate the top of your periscope while using it, to keep a lookout all around you.
- You can find PVC pipe at a hardware store or home improvement store.
Place a curved elbow joint pipe over each end of the pipe to make a periscope shape. Have the two openings point in opposite directions if you want to look around corners or over obstacles.^{[8]XResearch source}
These mirrors must be small enough to insert each one into one end of the pipe. This may be easier with a circular mirror, which you may be able to find at craft stores or online.
Use putty or strong double-sided tape to stick the mirror to the inside corner of the elbow joint with putty.^{[9]XResearch source} Look through that elbow joint, at the mirror you just inserted. Adjust the mirror until you see the base of the pipe at the opposite end, or remove the opposite elbow joint and adjust until you can see straight through the pipe.
Fix the mirror at the same 45º angle, so light reflected off one mirror will bounce through the pipe, hit the second mirror, and emerge through the other opening.^{[10]XResearch source}
Adjust the mirrors until you can clearly see through the periscope. Once the image is clear, attach the mirrors more firmly with several layers of packing tape, or with a specialized glue such as PVC adhesive or plastic epoxy.^{[11]XResearch source}

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Question
Which mirror is used to make a periscope?
Community Answer
The two mirrors work together to create a periscope. One mirror captures the image while the other reflects it back into your eye. You cannot have a periscope without one or the other mirror.
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How does a simple periscope work?
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The mirror at the top of the periscope captures the image of whatever you're pointing it at. The image is then reflected back into the bottom mirror. Your eye views the reflection in the bottom mirror.
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How can you make a kaleidoscope?
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You can learn how to make a kaleidoscope by following the instructions in this How.com.vn article: How to Make a Kaleidoscope.
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Tips

You can make small mirrors out of an old CD, but wear gloves and eye protection to protect yourself from splinters, and work under adult supervision. Heat the CD first with a hair dryer to make it less brittle, then score lightly and repeatedly with a craft knife until it is cut into the shape you want.^{[12]XResearch source}
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Use masking tape to seal the middle.
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Just use a cardboard box and a couple of mirrors. It doesn't matter if they're blurry, so long as you can see something. If not, then get clearer mirrors.
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