Question

find the power of concave lens of focal length 2 metre

Answer 1

answer is - 0.5 d . use the formula p=1/f in meter. Also the focal length of concave mirror is in negative

Answer 2

hey friend,
here's your answer,

as we know ,
power =1/focal length
P=1/2
P=0.5 D

now, as it's a concave lens which has diverging actions on ray of lights .
therefore, Power = - 0.5 D

Hope it helps you.....!!