A) 3eV
B) 1.2eV
C) 0.6V
D) 1.4V
Correct Answer: C
Solution :
Key Idea: Stopping potential stops the maximum kinetic energy electrons. From Einstein's photoelectric equation, we have \[{{E}_{k}}=hv-W\] where hv is energy of photon absorbed by the electron in the metal, W is the work function of the metal. Also the potential at which the photoelectric current becomes zero is called Stopping potential or cut-off potential. Since, the stopping potential stops the maximum energy electrons, it is a measure of the maximum kinetic energy of the electrons. Given, \[hv=1.8eV,\text{ }W=1.2eV\] \[\therefore \] \[{{E}_{k}}=1.8-1.2=0.6\,eV\] Thus, stopping potential \[=\frac{{{E}_{k}}}{e}=\frac{0.6\times 1.6\times {{10}^{-19}}}{1.6\times {{10}^{19}}}\] \[=0.6V\]
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