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 m
F=1P=1−0.25=−4 m
A converging lens has a focal length of 50 cm. The power of this lens is : (a) + 0.2 D (b) - 2.0 D (c) + 2.0 D (d) - 0.2 D
A diverging lens has a focal length of 0.10 m. The power of this lens will be : (a) + 10.0 D (b) + 1.0 D (c) - 1.0 D (d) - 10.0 D
Focal length of a concave lens is 400 cm, then power of the lens is: