Question

If a spherical lens has a power of, −0.25 D, the focal length of this lens will be (a) −4 cm
(b) −400 mm
(c) −4 m
(d) −40 cm

Answer 1

Answer:

-4 m

Explanation:

Power=1/focal length

therefore, focal length is inverse of power i.e. 1/(-0.25)=4 m

Remember that si unit of power is 1/meter