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) $5.68$
Concept. $\phi=\dfrac{hc}{\lambda}-eV_0$, in joules.
Step 1. Photon energy. $\dfrac{6.62\times10^{-34}\times3\times10^8}{331\times10^{-9}}=6.0\times10^{-19}$ J.
Step 2. Electron energy. $1.6\times10^{-19}\times0.2=0.32\times10^{-19}$ J.
Step 3. Work function. $5.68\times10^{-19}$ J.
Answer. Option C.
Solution by Sreeraj P, M.Sc Physics
