Questions

A periscope is an optical instrument that uses a system of prisms, lenses, or mirrors to reflect images through a tube.

Light from a distant object strikes the top mirror and is then reflected at an angle of 90 degrees down the periscope tube. At the bottom of the periscope, the light strikes another mirror and is then reflected into the viewer’s eye.

Hence, A periscope works by the principle of Total internal reflection.

By default, a real number is treated as a float variable.

A Match stick. 

You tear a match out of a matchbook and scratch the head to light it, then the red tip turns black from the flame.

In MS-Word, the Ruler function helps align the text, graphic, tables or other elements in your document.