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

$A$ radio transmitter operates at a frequency of $880 \ kHz$ and a power of $10 \ kW$. The number of photons emitted per second is .......

$A$ $10\, kW$ transmitter emits radio waves of wavelength $500\, m$. The number of photons emitted per second by the transmitter is of the order of

$A$ $160 \,W$ infrared source is radiating light of wavelength $50000 \,\mathring A$ uniformly in all directions. The photon flux at a distance of $1.8 \,m$ is of the order of ............. $m^{-2} s^{-1}$.

$A$ $100 \; W$ sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is $589 \; nm$.
$(a)$ What is the energy per photon associated with the sodium light?
$(b)$ At what rate are the photons delivered to the sphere?

$A$ photon in motion has a mass.