Solution
Related Formula
E = (hc)/(λ)Photoelectric effect condition: E ≥ W₀ λ ≤ λ₀
Core Logic
Calculate the threshold wavelength (λ₀) for the metal. If the incident wavelength λ is strictly greater than λ₀, the energy is insufficient, and the photoelectric effect will NOT occur.
Work function W₀ = 6.6 ~eV = 6.6 × 1.6 × 10⁻¹⁹ ~J.
Step 1: Calculate Threshold Wavelength
λ₀ = (hc)/(W₀) λ₀ = 6.6 × 10⁻³⁴ × 3 × 10⁸6.6 × 1.6 × 10⁻¹⁹ λ₀ = 3 × 10⁻²⁶1.6 × 10⁻¹⁹ = (3)/(1.6) × 10⁻⁷ ~m λ₀ = 1.875 × 10⁻⁷ ~m = 187.5 ~nmStep 2: Conclusion
For the photoelectric effect to not occur, the incident wavelength must be larger than 187.5 ~nm. Looking at the options, only 200 ~nm is greater than 187.5 ~nm.
Pattern Recognition
Use the highly efficient approximation E(eV) = 1240λ (nm). Threshold λ₀ = (1240)/(6.6) ≈ 187 ~nm. Any λ > 187 ~nm fails to eject electrons.
Chapter Mix
Class 12 Physics: Dual Nature of Radiation and Matter