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

Answer: (b). Einstein's equation: K = (hc)/(λ) - φ. K₁ = (hc)/(3λ₂) - φ, while K₂/3 = (hc)/(3λ₂) - φ/3. Since φ > φ/3, K₁ < K₂/3. So the answer is (b) K₁ < K₂/3.

The maximum kinetic energies of photoelectrons emitted are K₁ and K₂… | MHT CET 2026 (18 Apr, Shift 2)

Q24MHT CET 2026 · 18 APR · SHIFT 2Medium

Photoelectric Effect: Einstein's Equation

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

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Answer: (b)

Einstein's equation: $K = \frac{hc}{\lambda} - \phi$ .
$K_1 = \frac{hc}{3\lambda_2} - \phi$ , while $\frac{K_2}{3} = \frac{hc}{3\lambda_2} - \frac{\phi}{3}$ .
Since $\phi > \frac{\phi}{3}$ , $K_1 < \frac{K_2}{3}$ .
So the answer is (b) $K_1 < \frac{K_2}{3}$ .

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