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Building blocks of Matter | particles Classification | quark model | nuclear physics 15 | class 12 physics | fsc physics | elementary particles

welcome to candle academy Pakistan. This is lecture 15 of chapter 20 nuclear physics for 2nd year. In this lecture particle classification and elementary particles are explained.
Theory
When scientist came to know about atom they considered that atom is indivisible particle and it has no structure, as John Dalton atomic theory reveals, but crooks tube experiment of JJ Thomson discovered that there exist even smaller particle than atom in matter which carry negative charge. later on other particles, proton and neutrons were also discovered. After that scientist tried to develop atomic structure. In this regard different scientists proposed different atomic models, among which Niel Bohr atomic model was highly accepted which was a correction of Rutherford model. Later on Schordinger improved this model and scientist thought that electron proton and neutrons are elementary particles and these are made up of nothing. Soon after that positive and negative beta decay process urgegd scientist to research on protons and neutrons. in 1960 particle colliders were invented in which more than hundred subatomic particles were discovered.

Quark Model
In order to explain the existence of such huge number of subatomic particles a quark model was proposed. there are three generations of quarks. up and down quarks are first generation quarks, charm and strange or second generation where as top and bottom are third generation quarks. up and down quarks are basic and lighter particles. Every quark has its corresponding anti quark. Quarks carry the fractional charge of electron or proton.

Quarks as charge careers
up charm and top quark carry +2/3e where as down, strange and bottom quark carry -1/3e charge.

particle classification
There are two major classes of particles
Hadrons and Leptons
a. Hadrons
hadrons are the particles which are affected by strong nuclear force or in other words all the four forces are effective for hadrons. These are further classified into two branches barions and mesons.
Barions
Barions are made up of three quarks like proton is composed of two up and one down quark . Neutrons are made up of two down quark and one up quark.
Mesons
Mesons are made up of two particle, quark and anti quark pair.

leptons
leptons are the particles which are not affected by strong nuclear force but affected by electromagnetic force, weak nuclear force and gravitational force.
Leptons are the basic particles which have no structure. These are elementary particles. there are 6 Leptons electron, electron nutrino, muon, muon nutrino tau and tau nutrino. electron, muon and tau have negative charge where as their respective nutrinos have no charge and have very small mass, velocity nearly equal to that of light and pass through material without defloration.

standard model
there are six quarks and six leptons collectively called fermions and bounded by four types of force carriers called bosons. these include, gama photon, w boson z boson and gluon.


after completing this lecture students will be able to explain the following.
what is quark?
what is hadrons and leptons?
what is fermions and bosons?
what is mesons and baryons?
explain quark standard model.
what is particle classification?
explain elementary particles.


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