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Stuck here, help me understand: monochromatic light of wavelength 667 nm is produced by a helium neonlaser. The power emitted is 9 mW. The number of photons arriving per sec on the average at a target irradiated bt this beam is:

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 sec on the average at a target irradiated bt this beam is:

  • Option 1)

    3\times 10^{16}

  • Option 2)

    9\times 10^{15}

  • Option 3)

    3\times 10^{19}

  • Option 4)

    9\times 10^{17}

 
Answers (1)
164 Views

As we discussed in concept

photon -

A packet or bundle of energy is called a photon

-

 

 Power of EM wave is P=\frac{Nhc}{\lambda}

N = number of photon arriving per second

   = \frac{P \lambda}{hc}

N = \frac{9\times 10^{-3}\times 667\times 10^{-9}}{6.62\times 10^{-34}\times 3\times 10^{8}} = 3 \times 10^{16}

 


Option 1)

3\times 10^{16}

This option is correct.

Option 2)

9\times 10^{15}

This option is incorrect.

Option 3)

3\times 10^{19}

This option is incorrect.

Option 4)

9\times 10^{17}

This option is incorrect.

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