The number of photons emitted from a photocell by a source placed at a distance of $0.5 \ m$ is how many times the number of photons emitted by the same source placed at a distance of $1 \ m$?

$A$ photon,an electron,and a uranium nucleus all have the same wavelength. The one with the most energy is:

An electron-positron pair is created by $\gamma$-rays. What is the minimum energy of the $\gamma$-rays required for this process in $MeV$?

Given below are two statements:
Statement-$I$: Two photons having equal linear momenta have equal wavelengths.
Statement-$II$: If the wavelength of a photon is decreased,then the momentum and energy of the photon will also decrease.
In the light of the above statements,choose the correct answer from the options given below.

If $h$ is Planck's constant,the momentum of a photon with a wavelength of $0.01 \ \mathring A$ is .........

Calculate the energy of a photon having wavelength $\lambda = 1000 \, \mathring{A}$ in Joules.