Teacher Demo of periscope

A periscope is commonly used on submarines, where they are underwater and need to see what's going on above them without surfacing and giving away their position. They extend the periscope by poking a small tube-like device over the surface of the water while they view the situation.

How the periscope works is it has 2 mirrors placed at 45 degree angles to each other, as can be seen in the picture. This is a simplification of how the periscope works, but it will do for our example. (In submarines, they have a series of lenses to magnify the image over a longer distance.)