Question

How many diopters are there for for a converging lens with a focal length of 0.4m?
−2.5
−0.4
+0.4
+2.5

Answer 1

Answer on Question #46984, Physics, Optics

How many diopters are there for a converging lens with a focal length of $0.4\mathrm{m}$ ?

-2.5

-0.4

+0.4

+2.5

Solution:

A converging lens is said to have positive focal length. A converging lens causes exiting rays to be more convergent coming out than they were entering the lens.

The power of a lens is the inverse of the focal length.

$$P = \frac {1}{f}$$

where $P$ is in diopters and $f$ is in meters.

Thus,

$$P = \frac {1}{0 . 4} = 2. 5$$

Answer: +2.5