Q 12-11-038JEE MainJEE Main 2026 (5 Apr, Shift 1)Medium
Light source having wavelength $331$ nm is used to generate photo-electrons whose stopping potential is $0.2$ V. The work function of the used metal in the experiment is $\alpha \times 10^{-19}$ J. The value of $\alpha$ is ______. ($h = 6.62 \times 10^{-34}$ J s, $e = 1.6 \times 10^{-19}$ C and $c = 3 \times 10^8$ m/s)
Answer: (C) $5.68$
Photon energy: $\dfrac{hc}{\lambda} = \dfrac{6.62 \times 10^{-34} \times 3 \times 10^8}{331 \times 10^{-9}} = 6.0 \times 10^{-19}$ J.
Maximum KE $= eV_0 = 0.32 \times 10^{-19}$ J.
$\phi = 6.0 \times 10^{-19} - 0.32 \times 10^{-19} = 5.68 \times 10^{-19}$ J.
Solution by Sreeraj P, M.Sc Physics