If the focal length of a convex lens is 50 cm, which one of the following is its power?
+2 dioptre
+0•02 dioptre
-0•5 dioptre
+0•5 dioptre
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-2 – 2018
– The focal length must be expressed in meters when calculating power in dioptres.
– Given focal length f = 50 cm.
– Convert focal length to meters: 50 cm = 0.50 m.
– Power P = 1 / f (in meters).
– P = 1 / 0.50 m = 2 dioptres.
– A convex lens has a positive focal length and therefore a positive power.
– Convex lenses are converging lenses and are used to correct hypermetropia (far-sightedness).