Answer
a) $0.66m$
b) $0.08m, 0.41m, 0.62m$
Work Step by Step
(a) We know that
$V=\frac{U}{q}$
We plug in the known values to obtain:
$V=\frac{2.6\times 10^{-5}J}{6.2\times 10^{-6}C}$
$V=4.2V$
We can see from the graph that the position of the charge at which the potential is $4.2V$ is $0.66m$.
(b) We know that
$V=\frac{U}{q}$
We plug in the known values to obtain:
$V=\frac{4.3\times 10^{-5}J}{6.2\times 10^{-6}C}$
$\implies V=6.9V$
From the graph we can see that the value of the potential occurs at the three points: $0.08m, 0.41m, 0.62m$.
