Monochromatic light of wavelength 667 , nm is | vedclass

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(A) Given: Wavelength $\lambda = 667 \, nm = 667 	imes 10^{-9} \, m$. Power $P = 9 \, mW = 9 	imes 10^{-3} \, W$.Energy of a single photon $E = \fra

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$3 	imes 10^{16}$

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(A) Given: Wavelength $\lambda = 667 \, nm = 667 	imes 10^{-9} \, m$. Power $P = 9 \, mW = 9 	imes 10^{-3} \, W$.Energy of a single photon $E = \frac{hc}{\lambda}$.Using $h = 6.63 	imes 10^{-34} \, J \cdot s$ and $c = 3 	imes 10^8 \, m/s$:$E = \frac{6.63 	imes 10^{-34} 	imes 3 	imes 10^8}{667 	imes 10^{-9}} \approx 2.98 	imes 10^{-19} \, J$.The number of photons per second $n = \frac{P}{E}$.$n = \frac{9 	imes 10^{-3}}{2.98 	imes 10^{-19}} \approx 3.02 	imes 10^{16} \approx 3 	imes 10^{16}$ photons/sec.

Monochromatic light of wavelength $667 \, nm$ is produced by a helium-neon laser. The power emitted is $9 \, mW$. The number of photons arriving per second on average at a target irradiated by this beam is:

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