Question

which has greater power a convex lens of focal length 10 cm or 20 CM

Answer 1

Power = 1 / Focal length ( in m )

Focal Length 1 = 10 cm = 0.01 m

Power = 1 / 0.01 m = 100 / 1 = 100 D

Focal Length 2 = 20 cm = 0.02 m

Power = 1 / 0.02 = 100 / 2 = 50 D

Hence Focal length 1 has greater power than Focal length 2.

Alternate method :

We know that Power is inversely proportional to Focal length.

Hence more focal length implies less power. Hence Focal length of 10 cm has greater power than 20 cm.

Answer 2

Answer:

10 CM WILL HAVE A GREAT POWER