Fundamental interactions.

Fundamental interactions

There are four types of interaction between the elementary particles. These are

1) Gravitation interaction

The relative magnitude of gravitational interaction is 10⁻³⁹ and thus is the weakest interaction. The range of gravitation interaction is infinite. The particles exchange during gravitation interaction are gravitons. Every particle having mass is affected by gravitational interaction. It has characteristic time 10⁻¹⁶s and it has spin 2. Example of gravitational interaction is astronomical forces.

2) Electromagnetic interaction

The relative magnitude of electromagnetic interaction is 10⁻³. It is a long range interaction (infinite). The particles exchange during electromagnetic interactions are photons. The particles affected by electromagnetic interactions are charged particles. It has characteristic time 10⁻²⁰s and it has spin 1. Example of electromagnetic interaction is atomic forces.

3) Strong interaction

The relative magnitude of strong interaction is 1. It is a short range interaction (~10⁻¹⁵m). The particles exchange during strong interaction are pions, gluons and kaons. The particles affected during such interactions are hadrons. It has characteristic time 10⁻²³s and it has spin 1. Example of strong interaction is nuclear forces.

4) Weak interaction

The relative magnitude of weak interaction is 10⁻¹³ - 10⁻¹¹. It is a short range interaction (~10⁻¹⁶m). The particles exchange during weak interaction are intermediate bosons. The particles affected during such interactions are leptons and quarks. It has characteristic time 10⁻¹⁰s and it has spin 1. Example of weak interaction is forces involved in beta decay.

All these four interaction can account for all physical process in universe from hadrons to galaxies of stars.

Comments

LS coupling and jj coupling.

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Mass defect, packing fraction and binding energy.

Mass defect, packing fraction and binding energy: It was assumed that mass of the nucleus is equal to the mass of its constituents (i.e protons and neutrons). But experimentally it was found that the actual mass of the nucleus is less than the theoretical mass. Thus, the difference between the theoretical mass and experimental mass is called mass defect i.e ∆m={[Zmₚ + (A-Z)mₙ] - M} Where mₚ= mass of proton mₙ= mass of neutron M= actual mass of nucleus Z= atomic number A= mass number The ratio of mass defect and mass number (A) is called packing fraction (f) f = ∆m/A Thus packing fraction is the mass defect available per nucleon. The packing fraction explains the stability of the nucleus. The packing fraction may be positive, negative or zero. The positive value of packing fract...

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