\( = \frac{{1 \times {{10}^{ - 7}} \times 200 \times {{10}^{ - 9}}}}{{6.6 \times {{10}^{ - 34}} \times 3 \times {{10}^8}}} = 1 \times {10^{11}}\)

Number of electrons ejected \( = \frac{{{{10}^{11}}}}{{{{10}^3}}} = {10^8}\)

\(\therefore V = \frac{q}{{4\pi {\varepsilon _0}r}} = \frac{{({{10}^8} \times 1.6 \times {{10}^{ - 19}}) \times 9 \times {{10}^9}}}{{4.8 \times {{10}^{ - 2}}}} = 3\,V\)