A laser beam of output power ‘P’ consists only of wavelength $\lambda$. If Planck’s constant is h and the speed of light is c, then the number of photons emitted per second is

Given Data:

A laser beam of output power ‘P’ consists only of wavelength $\lambda$. Planck’s constant is h and the speed of light is c,.

Formula Used:

$P=n\times \frac{hc}{\lambda }$

Detailed Solution:

Power is total energy emitted per unit time = total number of photons emitted per unit time $\times$ energy of each photon.
$P=n\times \frac{hc}{\lambda }$
$n=\frac{P\lambda }{hc}$

Hence, the correct option is A.