The rest mass of the photon is

If the momentum of a photon is $p$,then its frequency is ........

$A$ photon has a wavelength of $3 \,nm$. Its momentum and energy, respectively, will be:
$[h = 6.63 \times 10^{-34} \,Js, c = 3 \times 10^8 \,m/s]$

Two sources of light emit with a power of $200 \ W$. The ratio of the number of photons of visible light emitted per second by each source having wavelengths $300 \ nm$ and $500 \ nm$ respectively,will be:

$A$ source $S_1$ is producing $10^{15}$ photons per second of wavelength $5000 \; \mathring{A}$. Another source $S_2$ is producing $1.02 \times 10^{15}$ photons per second of wavelength $5100 \; \mathring{A}$. Then,$(\text{power of } S_2) / (\text{power of } S_1)$ is equal to

The momentum of a photon having energy $hv$ is ............