In equation $P=Ec^{-1}$, where P is momentum, E is energy and c is the speed of light. In which of the following options, this equation is valid:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → for a photon but not for an electron
The equation $P=Ec^{-1}$ is valid for mass less particles. Such as photons, where the energy and momentum is related by $E=Pc$.