A spherical mirror is a part of a hollow glass sphere that is polished on one side.

The geometrical centre of a spherical mirror is called its pole.

An incident ray passing through the focus of a convex mirror goes undeviated after reflection.

A concave mirror is used in solar heaters.

A real image is always erect.

Light travels faster in the air than in water. 

The ray of light emerging out of a glass slab is always parallel to the incident ray.

A prism is a glass block that has a rectangular cross-section, formed by three triangular faces.

The angle through which the incident ray is deviated by the prism is called the angle of deviation.