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  4. The work function of a metallic surface is 5.01eV. The photo-electrons are emitted when light of wavelength 2000 mathringA falls on it. The potential difference applied to stop the fastest photo-electrons is:- [h = 4 . 14 × 10- 15 e V sec]

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Q. The work function of a metallic surface is $5.01eV.$ The photo-electrons are emitted when light of wavelength $2000\mathring{A} $ falls on it. The potential difference applied to stop the fastest photo-electrons is:-
$\left[h = 4 . 14 \times 10^{- 15} e V sec\right]$

NTA AbhyasNTA Abhyas 2020

Solution:

Energy of incident light $E=\frac{12375}{2000}=6.18eV$
According to relation $E=W_{0}+eV_{0}$
$\Rightarrow V_{0}=\frac{\left(E - W_{0}\right)}{e}=\frac{\left(\right. 6 . 18 e V - 5 . 01 e V \left.\right)}{e}=1.17V\approx1.2V$