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Photon flux (photons/sec) for 1 W of green light (λ = 550 nm):
A10²⁰ s⁻¹
B6 × 10²³
C10⁹
D2.77 × 10¹⁸ photons/sec (= P/E_photon)
Answer & Solution
Correct answer: D. 2.77 × 10¹⁸ photons/sec (= P/E_photon)
E_photon = hc/λ = 1240/550 ≈ 2.25 eV = 3.6 × 10⁻¹⁹ J. N/sec = 1 W / E = 1 / 3.6 × 10⁻¹⁹ ≈ 2.78 × 10¹⁸ photons/sec.
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