In photoelectric effect an em-wave is incident on a metal surface and… | JEE Main 2025 (23 Jan, Shift 2)

Q35JEE Main 2025 · 23 JAN · SHIFT 2Easy

Photoelectric Effect: Einstein's Equation

In photoelectric effect an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V, what is the wavelength of the em-wave? (Given $hc = 1242\text{ eV nm}$ where h is the Planck's constant and c is the speed of light in vacuum.)

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Answer: (c)

$E = \phi + eV_0 = 2.14 + 2 = 4.14\text{ eV}$
$\lambda = \frac{hc}{E} = \frac{1242}{4.14} = 300\text{ nm}$
So the answer is (c) 300 nm.

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