Question

if the power of a lens is -2D , so
A) it will have focal length of -50cm of a convex lens
B) it will have focal length of -50cm of a concave lens
C) it will have focal length of +50cm of a convex lens
D) it will have focal length of +100cm of a convex lens​

Answer 1

Answer:

B)  it will have focal length of -50cm of a concave lens

Explanation:

Power of a lens = reciprocal of focal length in meters

                          = 100/focal length in centimeters.

-2D = 100/f

f= 100/-2

f= -50 cm.

Since the focal length is negative, it is a concave lens.

So, If the power of a lens in -2D, it will have a focal length of -50 cm and will be a concave lens.