Question

Which of the following statements is true? 

(a) A convex lens has 4 dioptre power having a focal length of 0.25 m 

(b) A convex lens has –4 dioptre power having a focal length of 0.25 m 

(c) A concave lens has 4 dioptre power having a focal length of 0.25 m 

(d) A concave lens has –4 dioptre power having a focal length of 0.25 m

Answer 1

The answer is (a) A convex lens has 4 dioptre power having a focal length 0.25 m

Positive value for focal length indicates convex lens.