Answer : The radiation which is smallest in the size is, Gamma radiation.
Explanation :
Alpha particle : It is also known as alpha radiation or alpha ray that consists of 2 protons and 2 neutrons that are bound together into a particle that is identical to the helium nucleus. It is produced in the process of alpha decay.
Beta particle : It is also known as beta radiation or beta ray. During the beta decay process, a high energy and speed electron or positron are emitted by the radioactive decay of atomic nucleus.
Gamma particle : It is also a gamma radiation or gamma ray that is arising from the radioactive decay of atomic nuclei. It has shortest wavelength waves and imparts high photon energy can pass through most forms of matters because they have no mass.
The increasing order of the particle size of the alpha, beta and gamma particles will be :
Gamma particle < Beta particle < Alpha particle
Hence, the radiation which is smallest in the size is, Gamma radiation.
