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 $\alpha \times {10}^{-19}\mathrm{J}.$ The value of $\alpha$ is _______.

(h = 6.62 × 10⁻³⁴ Js, e = 1.6 × 10⁻¹⁹ C, c = 3 × 10⁸ m/s):

[JEE Main 2026, 5 Apr (Shift 1)]

Question

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 $\alpha \times {10}^{-19}\mathrm{J}.$ The value of $\alpha$ is _______.

(h = 6.62 × 10⁻³⁴ Js, e = 1.6 × 10⁻¹⁹ C, c = 3 × 10⁸ m/s):

[JEE Main 2026, 5 Apr (Shift 1)]

YESPYQ · Accepted Answer

Correct answer: c) 5.68. $\text{ (c) }ϕ=\frac{hc}{\lambda }-e{V}_{0}$ Substituting values, $\frac{hc}{\lambda }=\frac{6.62\times {10}^{-34}\times 3\times {10}^{8}}{331\times {10}^{-9}}=6\times {10}^{-19}\mathrm{J}$ $e{V}_{0}=1.6\times {10}^{-19}\times 0.2=0.32\times {10}^{-19}\mathrm{J}$ $ϕ=(6-0.32)\times {10}^{-19}=5.68\times {10}^{-19}\mathrm{J}$ Hence, the work function is $5.68\times {10}^{-19}\mathrm{J}$

Light source having wavelength 331 nm is used to generate photo- electrons whose stopping potential is 0.2 V. The work f…

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