Question

Find the power of a concave lens of focal length 2.5​

Answer 1

f = -2.5m

P = 1/f = -2/5 = -0.4D

Answer 2

Hey!! Here is your Answer!!

Focal length = 2.5 cm

focal length = 2.5*100 m

focal length = 250m

now

power = 1/f(in m)

power = 1/250

power = +0.004D.

Hope it helps you!!