Question

If the power of a lens is + 2d what is its focal length and its nature

Answer 1

Power = 2d
Focal length = 1/p
= 1/2 m = 100/2 cm
The lens is convex lens as focal length is positive
If u = -10 cm
f = 50 cm
1/f = 1/v - 1/u
1/50 = 1/v - 1/(-10)
1/50 = 1/v + 1/10
1/50 - 1/10 = 1/v
(1 - 5)/50 = 1/v
1/v = -4/50
v = -50/4 cm
As v is negative the image will form on the same side of object so nature of image is virtual and erect.
Hope it works :)

Answer 2

Explanation:

50 cm

power = 2 d

focal length = 1 / p

100/ 2 = 50 cm