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Photoelectric effect: when light of frequency ν falls on a metal of work function φ, KE of emitted electrons is:

AKE = hν - φ (if hν > φ, otherwise no emission)
BKE = φ
CKE = hν
DKE = hν + φ
Answer & Solution
Correct answer: A. KE = hν - φ (if hν > φ, otherwise no emission)
Einstein's photoelectric equation: KE_max = hν - φ. Photon energy hν first overcomes the work function φ; remainder becomes kinetic energy. No emission if hν < φ (regardless of intensity). Earned Einstein the 1921 Nobel Prize.
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