Periscope

A periscope is an optical instrument designed to allow an observer to see around corners.

Periscopes rely on optical prisms or bundles of optical fibers.

Submarines rely on periscopes to allow their officers to view the water's surface when they are submerged. Armored fighting vehicles, like tanks, are designed with periscopes, so their crew can see out, even after they close their armored hatches, when they anticipate being fired upon by an enemy. Military periscopes rely of solid optical prisms.

Medical personnel use instruments with long parallel bundles of optical fiber, which are flexible enough to be inserted into the human body. These instruments typically are named after the body part they are specifically designed to examine. For instance, a colonoscope is particularly designed to inspect the inside of the hollow organ known as the colon.