Q. Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively illuminate a metallic surface whose work function is 0.5 eV successively. Ratio of maximum speeds of emitted electrons will be
A) 1 : 5
B) 1 : 4
C) 1 : 2
D) 1 : 1
Explanation
[Solution from source] K(max) = hν − φ gives 1 − 0.5 = 0.5 eV and 2.5 − 0.5 = 2.0 eV. Since v ∝ √K, v₁ : v₂ = √0.5 : √2 = 1 : 2. Taking the ratio of photon energies (1 : 2.5) or of kinetic energies (1 : 4) are the traps. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.