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(B) The power $P$ of the laser is given by $P = nE$,where $n$ is the number of photons emitted per second and $E$ is the energy of a single photon.Ene

Vedclass · Accepted Answer

$10 	imes 10^{16}$

Vedclass · Answer

(B) The power $P$ of the laser is given by $P = nE$,where $n$ is the number of photons emitted per second and $E$ is the energy of a single photon.Energy of one photon is $E = h
u$,where $h = 6.6 	imes 10^{-34} \,J \,s$ and $
u = 5 	imes 10^{14} \,Hz$.$E = (6.6 	imes 10^{-34}) 	imes (5 	imes 10^{14}) = 33 	imes 10^{-20} \,J$.The power $P = 33 \,mW = 33 	imes 10^{-3} \,W$.Number of photons per second $n = P / E$.$n = (33 	imes 10^{-3}) / (33 	imes 10^{-20}) = 10^{17} = 10 	imes 10^{16}$ photons per second.Thus,the correct option is $B$.

$A$ laser produces a beam of light of frequency $5 \times 10^{14} \,Hz$ with an output power of $33 \,mW$. The average number of photons emitted by the laser per second is (Planck's constant $h = 6.6 \times 10^{-34} \,J \,s$)

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