Which of the following particles has a mass similar to that of an electron?

If the energy of a photon is expressed in units of $KeV$ and the wavelength in units of $\mathring{A}$,then the energy of the photon can be calculated by:

When a photon enters glass from air,which one of the following quantities does not change?

$A$ photon is associated with .........

The rest mass energy of an electron is $0.54 \, MeV$. If the velocity of the electron is $0.8 \, c$,then the kinetic energy $(K.E.)$ of the electron is .......... $MeV$.

The particle having zero rest mass is