Question

A convex lens has focal length +20cm , its power is ......
a) +5D
b) -5D
c) +0.05D
d) 100D
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Answer 1

Answer:

(a) +5D

Explanation:

Power = 1 / Focal length

Focal length = +20 cm

                     = +0.2 m

Power = 1 / +0.2

Power = +5 D

(a) +5D

Hope this helps! :)

Answer 2

Answer:

power= 0.05D

Explanation:

power of a lens is the reciprocal of the focal length

power = 1/20

= 0.05D