A Laser light of wavelength $660\,nm$ is used to weld Retina detachment. If a Laser pulse of width $60\, ms$ and power $0.5\, kW$ is used the approximate number of photons in the pulse are : [Take Planck's constant $h\, = 6.62\times10^{- 34}\, Js$]

  • [JEE MAIN 2017]
  • A

    $10^{20}$

  • B

    $10^{18}$

  • C

    $10^{22}$

  • D

    $10^{19}$

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