Monochromatic light of wavelength $667 \, nm$ is produced by a helium-neon laser. The power emitted is $9 \, mW$. The number of photons arriving per second on average at a target irradiated by this beam is:

The number of photons per second on an average emitted by a source of monochromatic light of wavelength $600 \, nm$,when it delivers a power of $3.3 \times 10^{-3} \, W$,is: $(h = 6.6 \times 10^{-34} \, Js)$

The momentum of a photon of energy $1 \text{ MeV}$ in $\text{kg-m/s}$ will be

The number of photons emitted per second by a bulb of $66 \ W$ power emitting waves of wavelength $600 \ nm$ is . . . . . . . $(h = 6.6 \times 10^{-34} \ J \cdot s)$

The momentum of a photon of light of frequency $f$ is . . . . . . .

Monochromatic light of wavelength $632.8 \; nm$ is produced by a helium-neon laser. The power emitted is $9.42 \; mW$.
$(a)$ Find the energy and momentum of each photon in the light beam.
$(b)$ 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 < target area).
$(c)$ How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?