Which of the following can make a parallel beam of light when light from a point source is incident on it ?
(a) Concave mirror as well as convex lens
(b) Convex mirror as well as concave lens
(c) Two plane mirrors placed at 90° to each other.
(d) Concave mirror as well as concave lens.
Explanation : When a point source is placed at the focus of a concave mirror or a convex lens, light after reflecting from the concave mirror and light
after refracting from a convex lens goes as a parallel beam.