How periscope works?

L.I To  understand how a periscope works.

Mr Johnston came and taught us what periscopes are,how they are used and who uses them. We found 

that the angle of incidence equals there angle of incidence equals the angel of reflection.That means if the light hits the mirror at 4.5 deggreesit reflects the light back.

It was fun because we get to write our names on the mirror.