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The magnetic field associated with a light wave is given, at the origin, by B=B₀[sin (3.14×10⁷)ct+sin (6.28×10⁷)ct]. If this light falls on a silver plate having a work function of 4.7 eV, what will be the maximum kinetic energy of the photo electrons? (c=3×10⁸ m s⁻¹, h=6.6×10⁻³⁴ J s)

Asked in JEE Main 9th Jan 2nd Shift 2019 · Work function and the photoelectric equation

Answer: (4) 7.72 eV

Step-by-step solution

The two angular frequencies are ω=3.14×10⁷c and 6.28×10⁷c.

Take the larger: ω=6.28×10⁷×3×10⁸=1.88×10¹⁶ rad s⁻¹.

E=ℏω=(6.6×10⁻³⁴)/(2π)×1.88×10¹⁶=1.98×10⁻¹⁸ J =12.4 eV.

Kₘₐₓ=12.4-4.7≈7.72 eV.

Why the other options are wrong

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