Example 1
A converging lens with f′ = 0.50 m has a vergence of +2.0 dioptres.
Mendeleev
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Physics tools › Optical power and focal length
Mendeleev · Physics
Optical power and focal length
Optical power is the reciprocal of focal length in metres. A shorter focal length means a larger magnitude of optical power.
Formula usedP = 1/f
Visual cue · lens
Calculate
Optical power and focal length
What do the symbols mean?
Poptical power
ffocal length
Two worked examples
Example 2
A +5 D lens has a focal length of 0.20 m.
Good to knowSigns matter in geometrical optics: converging lenses have positive optical power and diverging lenses negative optical power.