Subject: Physics
The branch of physics which deals with property, interaction and structure of elementary particles is called particle physics. Particle physics deals with smallest things in the universe whereas cosmology deals with the biggest thing in the universe.
The particles which are structureless, indivisible and not regarded as made up of some other particles is known as elementary particles. In 1897, after the discovery t electron by JJ Thomson, it was assumed that atoms were considered as fundamental particles of all the matter. Thomson’s discovery of electron and Rutherford’s discovery of atomic nucleus and proton in 1811 made it apparent that atom where not fundamental in the sense that they have an internal structure.
A brief description of some important particles is as follows:
Elementary particles can be classified on the basis of different properties of particles. They can be classified on the basis of mass (massless, light, intermediate and heavy), charge (positive, negative, neutral), spin or statistics (Bosons and Fermions), interaction (Gravitational, strong, weak and electromagnetic), lifetimes (stable and resonance).
The classification of massive elementary particles.
Mass: The elementary has always the same rest mass. The magnitude of the rest mass serves as the principle label which identifies the particles uniquely.
Charge: All known elementary particles have charge positive negative or zero. Further, the charge is always conserved in any collision process.
Average lifetime: All known elementary particles except photon, electron, proton and neutrinos are unstable and undergo decay into elementary particles of similar mass. The decay probability of a particular particle is, however, independent of the length of the time has lived.
Spin: Many elementary particles spin in a manner analogous to that of the earth on its axis, but with certain differences. The spin property forms a basis for the classification of elementary particles.
Interactions: Four kinds of interactions between elementary particles are known: gravitational, weak, electromagnetic and strong.
Reference
Manu Kumar Khatry, Manoj Kumar Thapa, et.al Principle of Physics. Kathmandu: Ayam publication PVT LTD, 2010.
S.K. Gautam, J.M. Pradhan. A text Book of Physics. Kathmandu: Surya Publication, 2003.
The branch of physics which deals with property, interaction and structure of elementary particles is called particle physics.
The particles which are structure less, indivisible and not regarded as made up of some other particles is known as elementary particles.
Electron is the first fundamental particle to be discovered and it revolves around the nucleus of an atom in different orbits.
Many elementary particles spin in a manner analogous to that of the earth on its axis, but with certain differences.
Four kinds of interactions between elementary particles are known: gravitational, weak, electromagnetic and strong.
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