Periscope
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![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/British_trench_periscope_Cape_Helles_1915.jpg/220px-British_trench_periscope_Cape_Helles_1915.jpg)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Periscope_simple.svg/220px-Periscope_simple.svg.png)
A periscope is an optical instrument that is used to watch a scene from cover. The classical design uses a number of mirrors or prisms, and is used in tanks and submarines.
A periscope is an optical instrument that is used to watch a scene from cover. The classical design uses a number of mirrors or prisms, and is used in tanks and submarines.