Question

what is the focal length of the lens with power minus 5.5 dioptres

Answer 1

Power = 1 / focal length ( in metre)

So, - 5.5 D = 1 / f

f = - 1 / 5.5 m

f = - 10 / 55 m

f = - 0.18 m = - 18 cm.

It is a concave lens of focal length 18 cm .

Answer 2

Answer:-0.18 m = - 18 cm

Explanation:

Power = 1 / focal length ( in metre)

So, - 5.5 D = 1 / f

f = - 1 / 5.5 m

f = - 10 / 55 m

f = - 0.18 m = - 18 cm.

It is a concave lens of focal length 18 cm