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MHT CET 2026 (15 Apr, Shift 2) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from MHT CET 2026 (15 Apr, Shift 2)

Q15MHT CET 2026 · 15 APR · SHIFT 2Medium

Photoelectric Effect: Einstein's Equation

When a metallic surface is illuminated with a radiation of wavelength ' $\lambda$ ', the stopping potential is 'V'. If the same surface is illuminated with radiation of wavelength $6\lambda$ , the stopping potential is $\left(\frac{V}{12}\right)$ . The threshold wavelength for the surface is

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Answer: (c)

$\frac{hc}{\lambda} - \phi = eV$ and $\frac{hc}{6\lambda} - \phi = \frac{eV}{12}$
Multiply the second by 12 and equate: $\frac{2hc}{\lambda} - 12\phi = \frac{hc}{\lambda} - \phi$
$11\phi = \frac{hc}{\lambda}$
$\lambda_0 = \frac{hc}{\phi} = 11\lambda$ . So the answer is (c) $11\lambda$ .

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