Find the focal length of a lens of power – 2.0 D. What type of lens is this?
Power of lens = –2.0 D
We know that,
Power of the lens = 1/Focal length
–2 = 1/Focal Length
Focal length = 1/(–2)
Focal length = –0.5 m
Since the focal length is negative, the lens is a concave lens.