Two point charges placed at a certain distance r in air exert a force F on each other. Then the distance r at which these charges will exert the same force in a medium of dielectric constnat K is given by

Options

A. r
B. `r//k`
C. `r//sqrtk`
D. `rsqrtk`

Answer

C

Explanation

`F=1/(4piepsilon_0) .q^2/(r^2)`
`F.=1/(4piepsilon_0) .q^2/(k(r.)^2)`
`F =F. implies 1/r^2 =1/(k(r.)^2) implies (r.)/r = sqrt(1//k)implies r. =r/(sqrtk)`