Calculation QM 3 (qm-03) Estimate (computing) the number of photons emitted by a bulb with 100 W per second in the visible range of light. Note 1: Simplify that λ = 500 nm

  Exercise: qm-03    

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Estimate (computing) the number of photons emitted by a bulb with 100 W per second in the visible range of light.
Note 1: Simplify that λ = 500 nm

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Solution:

1. E=h·f = h·c/λ
2. E_total = x·h·f = x·h·c/λ
       E_total equal to 100 W/s
       x is the number of particles at 500 nm
       x = E_total · λ / (h·c)
       x = 100J·500·10^-9 m / (6.026·10^-34 Js · 3.0·10⁸m/s)
       x = 2.5·10²⁰, i.e. about 1/1000 mol

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