Q: 11.4 (b) Monochromatic light of wavelength is produced by a helium-neon laser. The power emitted is .
How many photons per second, on the average, arrive at a target irradiated by this beam? Assume the beam to have uniform cross-section which is less than the target area),
Power of the light beam, P =9.42 mW
If n number of photons arrive at a target per second nE=P (E is the energy of one photon)