Question

When sunlight is concentrated on a piece of paper by a spherical mirror or lens, then a hole can be burnt in it. For doing this, the paper must be placed at he focus of:
(a) either a convex mirror or convex lens
(b) either a concave mirror or concave lens
(c) either a concave mirror or convex lens
(d) either a convex mirror or concave lens 

Answer 1

either a concave mirror or a convex lens

Both a concave mirror and a convex lens focus parallel light beams coming from a distant object onto the focus.