Photoelectric EffectHard
Question
A 200 W sodium street lamp emits yellow light of wavelength 0.6 μm. Assuming it to be 25% efficientin converting electrical energy to light, the number of photons of yellow light it emits per second is
Options
A.3 × 1019
B.1.5 × 1020
C.6 × 1018
D.62 × 1020
Solution
Energy emitted = 200 × 
= 50 W = 50 J / sec.
No. of photons =
= 50 W = 50 J / sec.No. of photons =
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