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JEE Main 202621 JanuaryMorning Shift
Exam
JEE Main
Year
2026
Date
21 January
Shift
Morning Shift
Subject
Physics
Chapter
Dual Nature of Matter

JEE Main 2026 · 21 January · Morning Shift · Physics · Dual Nature of Matter

A light wave described by E=60 [ (3 × 10^ 15 ) t+ (12 × 10^ 15 ) t]...

A light wave described by E=60E=60\left[\sin \left(3 \times 10^{15}\right) t+\sin \left(12 \times 10^{15}\right) t\right](inSIunits)fallsonametalsurfaceofworkfunction2.8eV.Themaximumkineticenergyofejectedphotoelectronis(approximately)(in SI units) falls on a metal surface of work function 2.8 eV. The maximum kinetic energy of ejected photoelectron is (approximately)\_\_\_\_eV.(h=6.6×10−34 JeV. \left(h=6.6 \times 10^{-34} \mathrm{~J}\right.. s. and \left.e=1.6 \times 10^{-19} \mathrm{C}\right)

Options

  1. A7.8
  2. B6.0
  3. C5.1
  4. D3.8

Correct answer

C. 5.1

Step-by-step solution

Light contains two frequencies: ω1=3×1015\omega_1 = 3 \times 10^{15} rad/s and ω2=12×1015\omega_2 = 12 \times 10^{15} rad/s
For maximum KE, use higher frequency ω2\omega_2.
Energy: E2=hω22π=6.6×10−34×12×10152πE_2 = \frac{h\omega_2}{2\pi} = \frac{6.6 \times 10^{-34} \times 12 \times 10^{15}}{2\pi}
=79.2×10−196.28=12.6×10−19= \frac{79.2 \times 10^{-19}}{6.28} = 12.6 \times 10^{-19} J =7.9= 7.9 eV
KE_\max = E_2 - \phi = 7.9 - 2.8 = 5.1 eV
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