2022-11-26

The number of photons emitted by a 5mW laser source operating at 632.8 nm is ? $×{10}^{16}$

revessatrP6

Expert

Every photon's energy is
$=E\frac{hc}{\lambda }$
$=\frac{\left(6.63×{10}^{-34}Js\right)×\left(3×{10}^{8}m{s}^{-1}\right)}{\left(632.8×{10}^{-9m}\right)}$
$=3.14×{10}^{-19}J$
The laser's energy output per second is $5×{10}^{-3}J$
Consequently, the rate of photon emission per second
$=\frac{5×{10}^{-3}J}{3.14×{10}^{-19}J}=1.6×{10}^{16}.$

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