\( \Rightarrow {K_{\max }} = E - {W_0} = 4.125\;eV - 1\;eV = 3.125\;eV\)
\( \Rightarrow \frac{1}{2}mv_{\max }^2 = 3.125 \times 1.6 \times {10^{ - 19}}\;J\)
\( \Rightarrow {v_{\max }} = \sqrt {\frac{{2 \times 3.125 \times 1.6 \times {{10}^{ - 19}}}}{{9.1 \times {{10}^{ - 31}}}}} \)\( = 1 \times {10^6}m/s\)
(Assume $\mathrm{h}=6.63 \times 10^{-34} \mathrm{~J} \mathrm{~s}, \mathrm{~m}_{\mathrm{e}}=9.0 \times 10^{-31} \mathrm{~kg}$ અને $\mathrm{m}_{\mathrm{p}}=1836$ $x$ $\mathrm{m}_{\mathrm{e}}$ ધારો)