A) \[8.4\times {{10}^{5}}m/sec\]
B) \[7.4\times {{10}^{5}}m/sec\]
C) \[6.4\times {{10}^{5}}m/sec\]
D) \[8.4\times {{10}^{6}}m/sec\]
Correct Answer: A
Solution :
By using \[E={{W}_{0}}+\frac{1}{2}mv_{\max }^{2}\] where \[E=\frac{12375}{2000}=6.18\ eV\] \[\Rightarrow 6.18\ eV=4.2\ eV+\frac{1}{2}mv_{\max }^{2}\] \[\Rightarrow 1.98\ eV=\frac{1}{2}mv_{\max }^{2}\] Þ \[1.98\times 1.6\times {{10}^{-19}}=\frac{1}{2}\times 9.1\times {{10}^{-31}}\times v_{\max }^{2}\] \[\Rightarrow {{v}_{\max }}=8.4\times {{10}^{5}}\ m/s\]
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