The momentum of a photon of energy \( 1.5 \) eV is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 8\times10^{-28}\,\mathrm{kg\,m\,s^{-1}} \)
A photon has zero rest mass, and its energy and momentum are related by \( E = pc \), so its momentum is \( p = E/c \).
\( E = 1.5\,\mathrm{eV} = 1.5\times1.6\times10^{-19}\,\mathrm{J} = 2.4\times10^{-19}\,\mathrm{J} \)
\( \displaystyle p = \frac{E}{c} = \frac{2.4\times10^{-19}}{3\times10^{8}} = 8\times10^{-28}\,\mathrm{kg\,m\,s^{-1}} \)