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

The momentum of a photon with energy $20 \, eV$ is

If the energy of the photon is increased by a factor of $4$,then its momentum

The minimum intensity of light to be detected by the human eye is $10^{-10} \ W/m^2$. The number of photons of wavelength $5.6 \times 10^{-7} \ m$ entering the eye,with a pupil area of $10^{-6} \ m^2$,per second for vision will be nearly:

$A$ $100\,W$ light source is emitting radiation of wavelength $5000\,\mathring{A}$. The rate of emission of photons is of the order of:

Which scientist discarded the postulate of ether?