$n$ photons of wavelength $\lambda$ are absorbed by a black body of mass $m$. The momentum gained by the body is

The number of photons emitted by a $10\,W$ bulb in $10\,s,$ if the wavelength of light is $1000\,\mathring{A},$ is:

The momentum of a photon of energy $1 \, MeV$ in $kg \, m/s$ will be:

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

There are two sources of light,each emitting with a power of $100 \, W$. One emits $X$-rays of wavelength $1 \, nm$ and the other visible light at $500 \, nm$. Find the ratio of the number of photons of $X$-rays to the photons of visible light of the given wavelength.

The photoelectric effect can be understood on the basis of