Question

The power of a lens is -2D . what will be its focal length?

Answer 1

P = 1/f

2 = 1/f

f = -0.5

Thanks

Answer 2

Given,
Power, P = -2D
Focal length, f = ?
We know that,
P = 1/f
-2= 1/f
-2f=1
f = 1/-2
f = -0.5
. ' . Required focal length is -0.5m.(' . ' SI unit of f is metre(m) )