$A$ photon of frequency $f$ has a momentum associated with it. If $c$ is the velocity of light,the momentum is:

An electron and a photon have the same wavelength of $10^{-9} \, m$. If $E$ is the energy of the photon and $p$ is the momentum of the electron,then the magnitude of $E / p$ (in $SI$ unit) is

If sources of ultraviolet $(\lambda \approx 400 \ nm)$,visible $(\lambda \sim 550 \ nm)$,and infrared $(\lambda \sim 700 \ nm)$ radiation each have a power rating of $100 \ W$,then the number of photons emitted per unit area per unit time is maximum for:

Number of photons of equal energy emitted per second by a $6 \ mW$ laser source operating at $663 \ nm$ is . . . . . . . (Given: $h=6.63\times10^{-34} \ J.s$ and $c=3\times10^{8} \ m/s$)

The momentum of a photon of energy $h\nu$ will be:

$A$ scientist claims to have a perfect technique in which he can spontaneously convert an electron completely into energy in the laboratory without any other material required. What is the conclusion about this claim from our current understanding of physics?