Q 12-11-011NEETNEET 2021Top questionEasy
The number of photons per second on an average emitted by the source of monochromatic light of wavelength $600$ nm, when it delivers the power of $3.3 \times 10^{-3}$ watt will be : ($h = 6.6 \times 10^{-34}$ J s)
Answer: (D) $10^{16}$
Concept. Photons per second $= \dfrac{P}{hc/\lambda}$.
Step 1. Photon energy. $\dfrac{6.6 \times 10^{-34} \times 3 \times 10^8}{600 \times 10^{-9}} = 3.3 \times 10^{-19}$ J.
Step 2. Number. $\dfrac{3.3 \times 10^{-3}}{3.3 \times 10^{-19}} = 10^{16}$.
Answer. $10^{16}$ (Option D).
Solution by Sreeraj P, M.Sc Physics