Question

What is the focal length of a lens if it has power P = 4D ? (A) 4 m (B) - 40 cm (C) - 0.25 m (D) - 25 m​

Answer 1

Answer:

Here, P is the power of the lens and f is the focal length of the lens in meter (m). Given, P = - 40 D. f = -0.025 m. Thus, the focal length of the lens is -0.025 m.