# how many photons are emitted per second by a 5mw laser source operating at 632.8nm?

Dear Student

Energy, E of the photon is given by -

E = $\frac{hc}{\lambda }$
So, E =

Now, the energy emitted per second by the laser source = 5 mW or 5 x 10-3 J

Thus, the total number of photons emitted per second =

Regards

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