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JEE Main 2022 (24 Jun, Shift 2) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from JEE Main 2022 (24 Jun, Shift 2)

Q92JEE Main 2022 · 24 JUN · SHIFT 2Easy

Photoelectric Effect: Einstein's Equation

The light of two different frequencies whose photons have energies 3.8 eV and 1.4 eV respectively, illuminate a metallic surface whose work function is 0.6 eV successively. The ratio of maximum speeds of emitted electrons for the two frequencies respectively will be:

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Answer: (b)

$\frac{1}{2}mv_{max}^2 = E - \phi$ , so $v_{max} \propto \sqrt{E - \phi}$ .
$K_1 = 3.8 - 0.6 = 3.2$ eV, $K_2 = 1.4 - 0.6 = 0.8$ eV
$\frac{v_1}{v_2} = \sqrt{\frac{3.2}{0.8}} = 2$
So the answer is (b) $2:1$ .

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