Q. What type of mirror is used by motorists to see the road behind them?
Answer: Convex
Notes: A convex mirror provides for a larger field of view than a plane mirror. This is why they are useful. They are used whenever a mirror with a large field of view is needed. For example, the passenger-side rear view mirror on a car is convex. For making sun glasses and telescopes also convex mirror is used. It is used as reflector in street lamps so as to diverge light over a large area.