A 200 W sodium street lamp emits yellow light of wavelength 0.6 μ m . Assuming it to be 25 % efficient in converting electrical energy to light, the number of photons of yellow light emitted per second is

Question

A 200 W sodium street lamp emits yellow light of wavelength 0.6 μ m . Assuming it to be 25 % efficient in converting electrical energy to light, the number of photons of yellow light emitted per second is, 1.5 × 10 20, 6 × 10 18, 62 × 10 20, 3 × 10 19

MARKS App · Accepted Answer

Efficient power p = N t × h c λ = 200 × 0.25 N t = 50 × λ h c = 50 × 0.6 × 10 - 6 6.6 × 10 - 34 × 3 × 10 8 = 1.5 × 10 20

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