A myopic person has a power of -1.25 Dioptre. What is the focal length and nature of his lens?
- 50 cm and convex lens
- 80 cm and convex lens
- 50 cm and concave lens
- 80 cm and concave lens
P = 1/f
f = 1/P = 1/1.25 = 0.8 m or 80 cm
Convex lenses, or converging lenses, have positive values, as they magnify objects. A diverging lens or concave lens, on the other hand, have a negative dioptre, since it makes objects appear smaller than they are.
The correct option is D.