What is the energy of a photon whose wavelength is $6840\,\mathring{A}$? (in $eV$)

Can a quantum of light be associated with a particle?

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

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

$A$ photon creates an electron-positron pair with equal kinetic energy. If the kinetic energy of each particle is $0.29 \ MeV$,the energy of the photon must be .......... $MeV$.

The ratio of the power of a light source $S_1$ to that of the light source $S_2$ is $2$. $S_1$ is emitting $2 \times 10^{15}$ photons per second at $600 \ nm$. If the wavelength of the source $S_2$ is $300 \ nm$,then the number of photons per second emitted by $S_2$ is . . . . . . $\times 10^{14}$.