What kinds of mirrors can I use to make a periscope?
You need two small mirrors, but they don't have to be identical.
If you have a rectangular mirror, or one with a handle, it's okay if part
of it sticks out the side of the carton. If your mirror is round, like the
mirror in a make-up compact, you may want to tape or glue it to a square
of cardboard before inserting it into the slot in the milk carton. If you
have a mirror with a magnifying side and a nonmagnifying side, have the
nonmagnifying side facing the hole.
To make a periscope from a 1-quart milk carton, your mirrors
must be smaller than 31/2 inches in at least one dimension. If the only
mirrors you can find are larger than that, you can use half-gallon milk
What if I want to use half-gallon milk cartons or some
When you are making a periscope, it's important to make
sure that your mirror is positioned at a 45-degree angle. If you use a wider
milk carton or some other box, just measure how wide your box is. Then measure
that same distance up the side of the box and make a mark. The line between
your mark and the opposite corner of the box will be at 45 degrees.
How does my
Light always reflects away from a mirror at the same angle
that it hits the mirror. In your periscope, light hits the top mirror at
a 45-degree angle and reflects away at the same angle, which bounces it
down to the bottom mirror. That reflected light hits the second mirror at
a 45-degree angle and reflects away at the same angle, right into your eye.
Can I make a periscope with a really long tube?
You can make your peri- scope longer, but the longer the
tube is, the smaller the image you'll see. Periscopes in tanks and submarines
have magnifying lenses between the mirrors to make the reflected image bigger.