MHT CET202520 Apr 2025Evening ShiftPhysicsDual Nature of MatterActual
A light of wavelength is incident on a photosensitive surface of negligible work function. The photoelectrons emitted from the surface have de-Broglie wavelength ₁ . Then ratio : ₁^2 is ( h = Planck's constant, c = velocity of light, m = mass of electron)
Options
- A4 mc : h
- B2 c: h
- C2 mc : h
- D2 mh : c
Correct answer
C. 2 mc : h
Step-by-step solution
The incident photon energy E = hc becomes the photoelectron's kinetic energy since the work function is negligible, so KE = hc . The photoelectron's kinetic energy also equals p^2 2m where p is its momentum. Equating these expressions: hc = p^2 2m Using the de Broglie relation ₁ = h p , we substitute p = h ₁ into the energy equation: hc = (h/ ₁)^2 2m = h^2 2m ₁^2 Solving for the ratio : ₁^2 : ₁^2 = 2mc h Thus : ₁^2 = 2mc : h , matching option C .