When two monochromatic lights of frequency, v and v/2 are incident on a photoelectric metal, their stopping potential becomes Vs/2 and Vs respectively. The threshold frequency for this metal is (a) 2v (b) 3v (c) 2/3 v (d) 3/2 v

Answer: (d). Einstein: hν = φ + eVs hν - φ = eVs/2 and hν/2 - φ = eVs hν/2 - φ = 2(hν - φ) ⇒ φ = (3hν)/(2) ν₀ = 3/2ν So the answer is (d) 3/2ν.

When two monochromatic lights of frequency, v and v/2 are incident on… | NEET 2022 (Phase 1)

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Photoelectric Effect: Einstein's Equation

When two monochromatic lights of frequency, v and $\frac{v}{2}$ are incident on a photoelectric metal, their stopping potential becomes $\frac{V_s}{2}$ and Vs respectively. The threshold frequency for this metal is

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Answer: (d)

Einstein: $h\nu = \phi + eV_s$
$h\nu - \phi = \frac{eV_s}{2}$ and $\frac{h\nu}{2} - \phi = eV_s$
$\frac{h\nu}{2} - \phi = 2(h\nu - \phi) \Rightarrow \phi = \frac{3h\nu}{2}$
$\nu_0 = \frac{3}{2}\nu$
So the answer is (d) $\frac{3}{2}\nu$ .

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