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Asked in GUJCET 2020 · Lens maker's formula and power
Given: f=+50 cm.
Idea: power is the reciprocal of the focal length with f in metres, P=1/f, and it keeps the sign of f.
First convert: f=+50 cm=+0.5 m.
P=1/(0.5)=+2 D.
The positive sign says the lens is converging, as a glass convex lens in air must be.
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