A $200\, W$ sodium street lamp emits yellow light of wavelength $0.6\, \mu m$. Assuming it to be $25\%$ efficient in converting electrical energy to light, the number of photon of yellow light it emits per second is

  • [AIPMT 2012]
  • A

    $1.5 \times 10^{20}$

  • B

    $62 \times 10^{20}$

  • C

    $3 \times 10^{19}$

  • D

    $6 \times 10^{18}$

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