Question

a 50 watt bulb emits monocromatic light of wavelength of 500 A. calculate the rate of emmision of quanta per second.​

Answer 1

The energy of one photon is

E=λhc

     =0.57×10−66.626×10−34Js×3×108m/s

     =3.487×10−19J .

25 watt corresponds to 25 J per second.

The number of photons emitted per second is 3.487×10−1925=7.17×1019/s.