Dual Nature of Matter

JEE Main level, single correct, medium

99 of 200

Question 99 of 200

A light wave described by E=60[sin⁡(3×1015)t+sin⁡(12×1015)t]E=60\left[\sin \left(3 \times 10^{15}\right) t+\sin \left(12 \times 10^{15}\right) t\right] (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 J\left(h=6.6 \times 10^{-34} \mathrm{~J}\right.. s. and e=1.6×10−19C)\left.e=1.6 \times 10^{-19} \mathrm{C}\right)

Show answer and solution

Answer: (C) 5.1

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
KEmax=E2−ϕ=7.9−2.8=5.1KE_{max} = E_2 - \phi = 7.9 - 2.8 = 5.1 eV

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.
See it move: Photoelectric effect and matter waves simulationDrag the sliders and watch the numbers in this question change.Revise Modern Physics firstFormula sheet, solved examples and the traps students fall into.

More Physics practice

JEE Main Physics practice question on Dual Nature of Matter (Photoelectric Effect), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.