The electrostatic field due to a point charge depends on the distance r as `(l//r^(2))`. Similarly, indicates how each of the following quantities depends on r : (a) Intensity of light from a point source (b) Electrostatic potential due to a point source (c) Electrostatic potential due to a distance r from the center of a charged metallic sphere of radius R `(r lt R)`.

Explanation

(a) For a point source, light intensity obeys inverse
square law, i..e, `1 prop (1)/(r^(2))`.
(b) In case of a point charge,
`V = (q)/(4pi in_(0) r) :. V prop r^(-1)`
(c ) In case of a charged conducting sphere for an internal point `(r lt R)`.
`V_(in) = V_(surface) = (q)/(4pi in R)` = constant.
`:. V prop r^(0),` i.e, V does not depend on r.