The maximum kinetic energies of photoelectrons emitted are K₁ and K₂ when lights of wavelengths λ₁ and λ₂ are incident on a metallic surface. If λ₁ = 3λ₂ then (a) K₁ = K₂/3 (b) K₁ < K₂/3 (c) K₁ = 3K₂ (d) 3K₁ = 2K₂

Answer: (b). K = (hc)/(λ) - φ, so K₁ = (hc)/(3λ₂) - φ. K₂/3 = (hc)/(3λ₂) - φ/3, which is larger than K₁. So the answer is (b) K₁ < K₂/3.

The maximum kinetic energies of photoelectrons emitted are K₁ and K₂… | MHT CET 2023 (11 May, Shift 1)

Q85MHT CET 2023 · 11 MAY · SHIFT 1Medium

Photoelectric Effect: Einstein's Equation

The maximum kinetic energies of photoelectrons emitted are $K_1$ and $K_2$ when lights of wavelengths $\lambda_1$ and $\lambda_2$ are incident on a metallic surface. If $\lambda_1 = 3\lambda_2$ then

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Answer: (b)

$K = \frac{hc}{\lambda} - \phi$ , so $K_1 = \frac{hc}{3\lambda_2} - \phi$ .
$\frac{K_2}{3} = \frac{hc}{3\lambda_2} - \frac{\phi}{3}$ , which is larger than $K_1$ .
So the answer is (b) $K_1 < \frac{K_2}{3}$ .

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