Number of photons per second \(=\frac{\text { Total energy emitted/sec }}{\text { Energy of one photon }}\)
Energy of one photon \(=\frac{h c}{\lambda}=\frac{h c}{632.2 \times 10^{-9}}\)
Energy per second emitted \(=5 \times 10^{-3} \,W\)
Total number of photons \(=\) Photons emitted per second \(\times\) Time
When time \(=2 \,s\)
(ઇલેક્ટ્રોનનું દળ $=9.1 \times 10^{-31} \,{kg}$ )