[Solution] $n = \frac{P\lambda}{hc} = \frac{3.3 \times 10^{-3} \times 6 \times 10^{-7}}{6.6 \times 10^{-34} \times 3 \times 10^8} = 10^{16}$ per second. Answer (2).
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.