A photodiode sensor is used to measure the output of a $300 \mathrm{W}$ lamp kept $10 \mathrm{m}$ away The sensor has an opening of $2 \mathrm{cm}$ in diameter. How many photons enter the sensor if the wavelength of the light is $660 \mathrm{nm}$ and the exposure time is $100 \mathrm{m} \mathrm{s}$. (Assume that all the energy of the lamp is given off as light and $\mathrm{h}=6.6\times {10}^{-34} \mathrm{J} \mathrm{s}$ )

• A

  $3.6\times {10}^{13}$
• B

  $2.8\times {10}^{13}$
• Correct answer
  C

  $2.5\times {10}^{13}$
• D

  $1.8\times {10}^{13}$

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