Monochromatic light of frequency 6.0 times 10 | vedclass

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Question

(D) The power $P$ of a monochromatic light beam is given by $P = N h 
u$,where $N$ is the number of photons emitted per second,$h$ is Planck's consta

Vedclass · Accepted Answer

$5 	imes 10^{15}$

Vedclass · Answer

(D) The power $P$ of a monochromatic light beam is given by $P = N h 
u$,where $N$ is the number of photons emitted per second,$h$ is Planck's constant,and $
u$ is the frequency.Given:Power $P = 2 	imes 10^{-3} 	ext{ W}$Frequency $
u = 6.0 	imes 10^{14} 	ext{ Hz}$Planck's constant $h \approx 6.63 	imes 10^{-34} 	ext{ J s}$Energy of one photon $E = h 
u = (6.63 	imes 10^{-34}) 	imes (6.0 	imes 10^{14}) 	ext{ J} \approx 3.978 	imes 10^{-19} 	ext{ J}$.Number of photons emitted per second $N = P / E$:$N = \frac{2 	imes 10^{-3}}{3.978 	imes 10^{-19}} \approx 0.5027 	imes 10^{16} \approx 5 	imes 10^{15}$ photons per second.Thus,the correct option is $D$.

Monochromatic light of frequency $6.0 \times 10^{14} \text{ Hz}$ is produced by a laser. The power emitted is $2 \times 10^{-3} \text{ W}$. The number of photons emitted,on the average,by the source per second is

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