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2.2 Devices with mirrors



The periscope is a device which allows one to see over or around obstacles. They are used in submerged submarines to have a view of the water surface.

The main components of a periscope are shown in the diagram below. The light enters one end of the device, makes a 90 degree turn when it reflects off a plane mirror set at a 45 degrees. The light travels down to the observer's level. A second mirror, also set at 45 degrees, directs the light through another 90 degree turn so that it travels towards the observer.