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Asked in GUJCET 2023 · Lens maker's formula and power
Given: P=-4.0 D.
Idea: P=1/f with f measured in metres, and the sign of P tells you which kind of lens it is.
f=1/(-4.0)=-0.25 m
Converting, f=-25.0 cm.
A negative focal length means the lens spreads a parallel beam, so it is a concave lens of focal length -25.0 cm.
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