The ratio of the power of a light source $S_1$ to that of the light source $S_2$ is $2$. $S_1$ is emitting $2 \times 10^{15}$ photons per second at $600 \ nm$. If the wavelength of the source $S_2$ is $300 \ nm$,then the number of photons per second emitted by $S_2$ is . . . . . . $\times 10^{14}$.

If the energy of a photon is $10\,eV$,then its momentum is

Write the characteristics of a photon or how can a photon of electromagnetic radiation be represented?

If we express the energy of a photon in $KeV$ and the wavelength in $\mathring{A}$,then the energy of a photon can be calculated from the relation:

Calculate the number of photons entering the eye of a duck per second,corresponding to the minimum intensity of white light $(\sim 10^{-10} \ W/m^2)$. Take the area of the duck's eye as $0.4 \ cm^2$ and the average frequency of white light as $6 \times 10^{14} \ Hz$.

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?