Sushil went to an eye specialist for a check-up. The doctor prescribed him to use spectacle lenses of $+0.5 \text{ D}$ power.
$(a)$ Name the defect of vision he is suffering from.
$(b)$ Find the focal length of the spectacle lens.

(N/A) The defect of vision is Hypermetropia (farsightedness).
$(b)$ The formula for focal length $f$ in meters is given by $f = \frac{1}{P}$,where $P$ is the power in Diopters $(D)$.
Given $P = +0.5 \text{ D}$.
$f = \frac{1}{0.5} = 2 \text{ m}$.
Therefore,the focal length of the convex lens is $2 \text{ m}$.