A 150 watt bulb emits light of wavelength 6600 Å and only 8 % of the energy is emitted as light. How many photons are emitted by the bulb per second?

Step-by-step solution

Power of the bulb =150 ~W =150 ~J ~s ⁻¹ As only 8 % of the energy is emitted as light so, the total energy emitted per second = 150 ~J 8 100 =12 ~J Energy of one photon, E=h v= h c aligned &= (6.626 10⁻³⁴ Js ) (3 10⁸ ~ms ⁻¹ ) 6600 10⁻¹⁰ ~m &=3.0118 10⁻¹⁹ ~J aligned Number of photons emitted per second = 12 ~J 3.0118 10⁻¹⁹ ~J =3.98 10¹⁹ 4.0 10¹⁹