A) 4.9V
B) 3.0V
C) 2.0V
D) 1.0V
Correct Answer: C
Solution :
Key Idea: In photoelectric effect energy is conserved. In photoelectric effect Einstein's equation is given by. Photon energy\[=KE\]of electron + work function i.e., \[hv=e{{V}_{s}}+h{{v}_{0}}\] where\[{{V}_{s}}\]is stopping potential and\[{{v}_{0}}\]is the threshold frequency. \[\therefore \] \[{{V}_{s}}=\frac{h}{e}(v-{{v}_{0}})\] ...(i) Given, \[{{v}_{0}}=3.3\times {{10}^{14}}Hz,v=8.2\times {{10}^{14}}Hz,\] \[h=6.6\times {{10}^{-34}}J-s.\] \[e=1.6\times {{10}^{-19}}C\] Substituting the values in Eq. (i), we get \[{{V}_{s}}=\frac{6.6\times {{10}^{-34}}\times (8.2\times {{10}^{14}}-3.3\times {{10}^{14}})}{1.6\times {{10}^{-19}}}\] \[=\frac{6.6\times 4.9}{1.6}\times {{10}^{-1}}=2.0V\]
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