Optical power

Z=\dfrac{1}{f}

Result unit: D (dioptre = 1/m)

What it describes

The reciprocal of the focal length; the greater it is, the more strongly the lens converges light.

Z

optical power

[D]

f

focal length

[m]

The shorter the focal length, the more strongly the lens bends the rays — a greater optical power. Converging lenses have

Z>0

, diverging ones

Z<0

Choosing glasses (diopters); when combining lenses, we add their powers.

A lens with a focal length of 0.25 m. Calculate the optical power.

Substitution

f=0.25

Result

Z=\dfrac{1}{0.25}=4

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