Question

power of a lens is found to be +2.5 diopter . what kind of lens is it

Answer 1

Answer:

Reciprocal of focal length(in meter) is called diopter. So,

1 diopter = 1/1(m)

2.5 diopter = 1/x , x=1/2.5 where x is focal length in meter.

From here x=40cm. So the answer of your question is 40 cm.

In photography the focal length of any lense is generally measured in millimeters. So the 2.5 diopter is equivalent to 400mm.