A laser light of wavelength $660\mathrm{\hspace{0.17em}}\mathrm{nm}$ is used to weld Retina detachment. If a laser pulse of width $60\mathrm{\hspace{0.17em}}\mathrm{ms}$ and power $\mathrm{0}.5 \mathrm{kW}$ is used, the approximate number of photons in the pulse are (Take Planck's Constant, $h=6.62\times {10}^{-34}\mathrm{\hspace{0.17em}}\mathrm{J} \mathrm{s})$

• A

  ${10}^{22}$
• B

  ${10}^{19}$
• Correct answer
  C

  ${10}^{20}$
• D

  ${10}^{18}$

Hence, the correct answer is option: 'C'.