Question

the power of the lens is -40 d what is its focal length​

Answer 1

Answer:

Focal length f=

Power

1

∴ f=

−2

1

=−0.5 m

So, focal length of lens is 0.5 m.

Answer 2

Answer:

    -2.5cm

Explanation:

power of lens is -40

Since power is negative its a concave lens

Power = 1 / focal length

-40 = 1 / focal length

focal length = 1 / -40

focal length = -0.025m = -2.5cm