To solve this problem, we need to find the number of photons emitted per second by a source of monochromatic light.$\\$Given:$\\$• Wavelength $\lambda = 600$ nm$= 600 \times 10^{-9}$ m$\\$• Power $P = 3.3 \times 10^{-3}$ watt$\\$• Planck's constant $h = 6.6 \times 10^{-34}$ Js$\\$First, we calculate the energy of a single photon using the formula:$\\ E = \frac{hc}{\lambda} \\$Where:$\\$• $c = 3 \times 10^8$ m/s (speed of light)$\\$Substitute the known values:$\\ E = \frac{6.6 \times 10^{-34} \times 3 \times 10^8}{600 \times 10^{-9}} \\$Simplify the expression:$\\ E = \frac{6.6 \times 3 \times 10^{-34 + 8 + 9}}{600} \\ E = \frac{19.8 \times 10^{-17}}{600} \\ E = 3.3 \times 10^{-19}$ J$\\$Now, we find the number of photons emitted per second using the formula:$\\ n = \frac{P}{E} \\$Substitute the known values:$\\ n = \frac{3.3 \times 10^{-3}}{3.3 \times 10^{-19}} \\$Simplify:$\\ n = \frac{3.3}{3.3} \times 10^{-3 + 19} \\ n = 1 \times 10^{16} \\$Therefore, the number of photons emitted per second is $10^{16}. \\$This corresponds to Option 3.