A doctor has prescribed a corrective lens of power

Question.
A doctor has prescribed a corrective lens of power $+1.5$ D. Find the focal length of the lens. Is the prescribed lens diverging or converging ?

solution:

Given, power, $\mathrm{P}=+1.5 \mathrm{D}$

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

or $f=\frac{1}{P}=\frac{1}{+1.5}=\frac{10}{15}=+\frac{2}{3}$

or $\mathrm{f}=+0.66 \mathrm{~m}=+66 \mathrm{~cm}$

The lens is a convex (or converging) lens.

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