Question

15. Which of the following statements is true?
(A) A convex lens has 4 dioptre power having a
focal length 0.25 m
(b) A convex lens has - 4 dioptre power having a
focal length 0.25 m
(c) A concave lens has 4 dioptre power having a
focal length 0.25 m
(d) A concave lens has 4 dioptre power having a
focal length 0.25 m​

Answer 1

A) is correct focal length of convex lens is always positive so 0.25m
Power=1/f(m) 1/0.25
=4dioptre
So A is correct
Thanks