Question

A sodium lamp of 10 W emits light
of wavelength 5896 ARMSTRONG. Assume that 66% of the
consumed energy is converted into light, then find the
number of photons emitted per Second?​

Answer 1

P=10W

η=66%

Energy used per sec:

10 x 0.66=6.6J

λ=5896A

E=hc/λ

E=(6.62 x 10⁻³⁴ x 3 x 10⁸)/(5896 x 10⁻¹⁰)

E=0.0033x 10⁻¹⁶J

The number of photons(n)=(Energy used per sec)/E

n=6.6/0.0033 x 10⁻¹⁶

n=2000x 10¹⁶=2000 x 10¹⁵=2 x 10¹⁸