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JEE Main 2022 (28 Jul, Shift 2) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from JEE Main 2022 (28 Jul, Shift 2)

Q91JEE Main 2022 · 28 JUL · SHIFT 2Easy

Photoelectric Effect: Einstein's Equation

Two streams of photons, possessing energies equal to five and ten times the work function of metal are incident on the metal surface successively. The ratio of maximum velocities of the photoelectron emitted, in the two cases respectively, will be

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Answer: (c)

$\frac{1}{2}mv_{max}^2 = E - \phi$ , so $v_{max} \propto \sqrt{E - \phi}$ .
$K_1 = 5\phi - \phi = 4\phi$ , $K_2 = 10\phi - \phi = 9\phi$
$\frac{v_1}{v_2} = \sqrt{\frac{4}{9}} = \frac{2}{3}$
So the answer is (c) $2:3$ .

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