Question

find the focal length of a lens of power , -2 D .what type of lens is this ??
answer fast...

Answer 1

P=1/f(in m)
Now,
-2=1/f....
1=-2f .
1/-2=f..
therefore focal length will be 1/-2 m

Answer 2

hey.. here's ur answer,

the power of this kens has a negative sign, so this is a concave lens .

Now,
power, P = 1/ f

-2 = 1/ f

f = -1 / 2 m

or ,
f = -1 / 2. × 100

so, focal length of lens , f. = -50 cm.

hope it might be helpful !!