optics
...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 your box. 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 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. Can I make a periscope with a really long tube? You can make your periscope 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. Real life applications using the periscope -In tanks and submarines Background information about the periscope The periscope is the eye of the submarine. It was invented and developed solely for the purpose of providing a means to view the surface without fear of detection by surface craft. While it is primarily simple in principle, actually it is a complicated piece of apparatus. It is probable that all the navies of the world have similar instruments with only minor variations. The earliest submarines were built without provision for periscopes and therefore, when submerged, were forced to grope their way blindly. In 1854 Marie Davey, a Frenchman, designed a sight tube for a submarine. This tube contained two mirrors, one above the other, held at a 45 degree angle and facing in opposite directions. These, while providing some degree of sight to the submerged vessel, were faulty at best and, in 1872, prisms were substituted for mirro...