Answer: Option (d) is the correct answer.
Explanation:
An atom consists of three subatomic particles which are protons, electrons and neutrons.
Whereas a smallest quantum of electromagnetic radiation is known as photon. These remain always in motion and they travel at constant speed in a vacuum.
Mass of an electron is [tex]9.1 \times 10^{-31}[/tex] kg
Mass of a proton is [tex]1.67 \times 10^{-27}[/tex] kg
Mass of a neutron is [tex]1.67 \times 10^{-27}[/tex] kg
On the other hand, a photon is mass less.
Hence, we can conclude that out of the given options photon is the particle which has the smallest mass.
