NEET 2021 · PhysicsMatter wavePrevious Year Question
An electromagnetic wave of wavelength λ is incident on a photosensitive surface of negligible work function. If a photoelectron of mass m emitted from the surface has de Broglie wavelength λ_d, then:
Answer: (A) λ = (2mc/h)λ_d². Answer: (a) λ = (2mc/h)λ_d² Solution: Photon energy goes fully into electron KE (φ ≈ 0): hc/λ = p²/2m = h²/(2mλ_d²).
- A.λ = (2mc/h)λ_d²✓
- B.λ = (2h/mc)λ_d²
- C.λ = (m/hc)λ_d²
- D.λ = (mc/h)λ_d²
Correct Answer
(A) λ = (2mc/h)λ_d²
Solution & Explanation
Answer: (a) λ = (2mc/h)λ_d² Solution: Photon energy goes fully into electron KE (φ ≈ 0): hc/λ = p²/2m = h²/(2mλ_d²). Solve: λ = (2mc/h)·λ_d².
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