A photoelectric surface is illuminated successively by monochromatic… | MHT CET 2026 (19 Apr, Shift 1)

Q14MHT CET 2026 · 19 APR · SHIFT 1Medium

Photoelectric Effect: Einstein's Equation

A photoelectric surface is illuminated successively by monochromatic light of wavelength $\lambda$ and $(\lambda/3)$ . If the maximum kinetic energy of the emitted photo electrons in the second case is $4$ times that in the first case, the work function of the surface of the material is ( $h$ = Planck's constant, $c$ = speed of light)

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Answer: (b)

$K_1 = \frac{hc}{\lambda} - \phi$ , $K_2 = \frac{3hc}{\lambda} - \phi$ , with $K_2 = 4K_1$
$\frac{3hc}{\lambda} - \phi = \frac{4hc}{\lambda} - 4\phi \Rightarrow 3\phi = \frac{hc}{\lambda}$
$\phi = \frac{hc}{3\lambda}$ . So the answer is (b).

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Photoelectric Effect: Einstein's Equation question from MHT CET 2026 (19 Apr, Shift 1)

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