To enhance the discussion on nuclear and plasma Physics

Hullo once

2008-09-08T00:25:00.000-07:00

I want to discuss now on why the things should be exposed to the public.
The public is always responsible for the maintainance of the world. He must be responsible to do so. They must to know the current affairs and recent trends on scientific development and they must concern how to develop the current situations more manageable frames and ways. They must think themselves responsible for all the good or bad things happening, the risks and hazards of recent and current practices.
I think you all love to discover yourself and try to think in a more different track.

THE FUNDAMENTAL FORCES IN NATURE

2008-08-27T01:01:00.000-07:00

Particles in nature are subject to four fundamental forces. In order of decreasing strength they are: Strong force, the electromagnetic force, The weak force and the gravitational force.
Strong force is responsible for binding quarks tightly together to form Protons, neutrons and other heavy particles. It is extremely short range force.
Electromagnetic force binds the electrons and protons within atoms and molecules to form ordinary matter. It is approximately two orders of magnitude weaker than the strong force. It is a long range force that decreases in strength as the inverse square of the distance (separation between the interacting particles).
The weak force is a short range force that accounts for the beta-decay of nuclei and the decay of heavier quarks and leptons.
Scientists now believe that the weak and electromagnetic forces are two manifestations of a unified force, The Electroweak Force.
The Gravitational force is a long range force, which has very small strength (about 10^-43 times) that of strong force. Although this interaction holds the planets, stars and galaxies together, it's effect on elementary particles is negligible.
Classically, the entity, that is responsible for transmitting a force from one particle to another particle is called Field. The field can carry energy and momentum from one particle to the other.
According to quantum field theories, the energy and momentum of all fields are are quantised, and the quantum that carries a chunk of momentum and energy from one type of particles to another is called a Field particle.
In particle physics, interactions between particles are described in terms of exchange of field particles or quanta, which are all Bosons. In the case of electromagnetic interaction, the field particleare photons. In other words, the electromagnetic forces are mediated by photons (which are considered quanta of the electromagnetic field).
Likewise, the strong force is mediated by gluons, weak force is mediated by W+- & Zo bosons and gravitational force is mediated by gravitational quanta, called gravitons.

Fermions and Bosons

2008-08-27T00:30:00.001-07:00

The results of various experiments show that all particles which have odd half integral spins (1/2, 3/2, ...) have wave functions that arenantisymmetric to an exchange of any pair of them. Such particles including electron, proton and neutrons obey the Pauli exclusion principle when they are in the same system. i.e. when they move in a common force field, each of them must be in a different quantum state. These type of particles, the behaviour of which is governed by Fermi-Dirac statistics are called Fermions. Only one fermion can exist in a particular quantum state of the system.
The particles whose spins are 0 or an integer, having wave functions that are symmetric to an exchange of any pair of them, including Photons, Alpha particles and Helium atoms, do not obey the Pauli exclusion principle. The behaviour of systems of them (such as a photon in a cavity) is governed by Bose-Einstein Statistics and are called Bosons.
As a wave function of this type is symmetric, any no. of bosons can exist in the same quantum states of the system.

Positron and other Antiparticles

2008-08-21T23:30:00.000-07:00

Positrons: In the 1920sthe English theoretical physicist Paul Adrian Maurice Dirac (1902-1984) developed a version of quantum mechanics that incorporated special relativity. Dirac's theory automatically explained the origin of the electron spin and it's magnetic moment. However, it also presented a major difficulty. Dirac's relativistic wave equation required solutions corresponding to both positive and negative energies for free electron.
But if negative energy states existed, one would expect an electron in a state of positive energy to make a rapid transition to one of these lower energy states, emitting a photon in the process.
When the enough energy is supplied to excite the electron to a positive energy state, one of the negative energy state becomes vacant leaving a hole in the sea of filled states. The hole can react to the external forces and is observable and reacts in the similar way way to that of electron, except that it has a positive charge-it has a positive charge-it is antiparticle to the electron and is called positron
Positron has a rest energy of 0.511 MeV and a positive charge of +1.60* 10^-19C
While examining tracks created in a cloud chamber by electronlike particles of positive charge, Carl Anderson (1905-1991) observed positron in 1932 and awarded Nobel prize for this achievement in 1936.
Other antiparticles: Prior to 1953, on the basis of Dirac theory, it was expected that every particle had a corresponding antiparticle, but the antiparticle of proton and neutron ,antiproton and antineutron respectively had not been detected experimentally.
In 1955 a team led by Emilio Segre (1905-1989, Italian-American) and Owen Chamberlain (1920- American) used the Bevatron particle accelerator at the university of California, Berkeley, to produce both antiproton and antineutrons. They thus established with certainty the existense of antiparticles. (for this they received a Nobel Prize in 1959)
It is now accepted that every particle has a corresponding antiparticle of equal mass and spin and of equal and opposite charge, magnetic moment and strangeness. The only exceptions to these rules for particles and antiparticles are the neutral photon, pion and eta,each of which is it's own antiparticle.

Hadrons

2008-08-20T23:48:00.001-07:00

The Mesons and baryons are collectively called hadrons. The proton is a baryon with two upquarks and two down quarks.
Hundreds of hadrons have been observed. Other than the protons and neutrons, all of them have short half lives, less than 0.1 microsecond, for the longest lived ones.
A neutrino inside a nucleus can be stable, but an isolated is unstable decaying with a halflife of 10.2 minute into a proton, an electron and an antineutrino.
The proton is considered stable, with half life at least 10^29 years,

Quarks

2008-08-20T23:24:00.000-07:00

The protonsand neutrons have internal structure and thus are not fundamental particles. Each proton or neutron contains three quarks, which are fundamental particles. Their existense is proposed independently in 1963 by Murray Gell-Mann and George Zwig. Among them, Gell-Mann proposed the name quark.
An isolated quark has never been observed, it is considered impossible (even in Principle) because of strong interaction of the field.
Although three quarks were originally proposed, they are now known to be six with corresponding antiquark each with the same mass and opposite electric charge.
A bound quark-antiquark pair is called Mesons and a bound triplet of quarks and antiquarks is called a baryon; a bound system of four quarks and an antiquark has been recently observed, called pentaquark, a new baryon.

Leptons

2008-08-20T22:45:00.000-07:00

Protons and Neutrons are composed of quarks but not any experiment has suggested that the electron also has any internal structure. So electrons are considered leptons.
The six leptons (and their antiparticles) are grouped into three generations, each having one particle with charge -e and uncharged neutrino. The masses increase from one generation to other. Ordinary matter contains only first generation leptons.
Electrons are a basic building block of atoms, the positron (+e) is the antiparticle of electron and is emitted in beta+ decay, along with electron neutrino Ve. In beta(-) decay an electron antineutrino is emitted in addition to the electron. Electron neutrino and antineutrinos are also released in nuclear fusion. Earth is bathed in a steady stream of billion of neutrinos per square centimeter of cross sectional area per second from the fusion reaction taking place in Sun's interior.
Neutrons are difficult to observe as they can pass through matter. They are thought as massless for a long time but proven to be false. There are more neutrinos in the universe than all of the other leptons and quarks combined.
Muons are the first second generation particlesto be observed. Cosmic rays- stream of energetic particles (mostly protons), travelling from outer space-continually bombarded with Earth's upper atmosphere. The cosmic ray particles usually energies in GeV range, some had been observed upto 10^11 GeV range.
Neither the Muons nor the the Tau is stable, they are considered fundamental or elementary particles as they do not appear to have any substructure. A neutrino can transform from one type of neutrino to another. This effect is called neutrino oscillation.
Let's make our planet livable for our offsprings

Elementary particles

2008-08-20T21:46:00.000-07:00

Ordinarily matter is considered to be composed of Protons , Neutrons and Electrons, which, at first seem enough to account for the structure of the universe. However several other particles like neutrinos, pions, photons with their definite and specific role are also discovered.

Hundreds of elementary particles have been discovered, all of which decay rapidly after being created in high energy collisions between other particles.

Elementary particles fall into two classes, Leptons and Hadrons, depending on whether they respond to the strong interactions (Hadrons) or do not (Leptons).

It is clear that leptons are more elementary than hadrons,which are composites of a far smallerno. of rather unusual particles called quarks, that have not been detected in isolation (and probably will never be).

Leptons (greek: 'light' or 'soft') are the simplest particles and truely elementary. They have left no hint of internal structure or even of extension in space. Leptons are affected only by electromagnetic (if charged), weak and gravitational interaction. The electrons and e-neutrinos with other four (Muon, Mu-neutrino, Tau and Tau-neutrino) are leptons.

Hadrons (Greek: 'heavy', 'strong') are subject to the strong interaction as well as to the others. They occupy space and seem to be little over 1fm across. Hadrons are composed of either two or three quarks, which like leptons are structureless and as close to being point particles.

Hadrons consisting of three quarks such as proton and neutron are called baryons and consisting two quarks such as pions are called mesons.

Quarks have charges, but they are combined to form chargeless hadrons. Quarks are never been observed outside of hadrons. The strong force that acts between hadrons is the external manifestation of the more basic interactions among the quarks they contain and is mediated by the exchange of mesons.

Hadrons: Particles subject to strong interaction.

Quarks: The ultimate constituents of hadrons.

Special Theory of Relativity

2008-08-20T01:03:00.000-07:00

Introduction: The special theory of relativity was proposed by Albert Einstein in 1905 and is considered as second great theory of 20th century physics. Theory is indespensible to the development of atomic and nuclear physics.
This theory depends upon two closely related ideas, the first is the variation of mass of a particle with it's velocity and the second is that of the proportionality between mass and energy. Which is expressed by the following equation:
E=mc^2
which occupies a prominient role in the physics of this day.
This equation is also used in nuclear physics too.
1> The variation of mass with velocity:
(negative results of Michelson-Morly experiment: (reference 1))
Albert Einstein---------------------->

The classical mechanics could not deal the negative results of Michelson-Morley experiment. The problems raised by Michelson-Morley experiment and the requirement of invariance were solved by Einstein in 1905.

According to Einstein, only relative velocities can be measured, and it is impossible to ascribe any absolute meaning to different velocities.so the general laws of physics must be independent of the velocity of the particular system of coordinates used in their statements, because if these were not so, it would be possible to ascribe some absolute meaning to different velocities. The requirement is that then equations of a physical theory be invariant with respect to coordinate systems moving with different velocities.

Postulates of special theory of relativity:

There are two postulates considered by Einstein in drawing the special theory of relativity. Due to mathematical restrictions to the consideration of reference systems moving at constant velocity relative to each other, the first postulate is given as: " The laws of physical phenomena are the same when stated in terms of either of two reference systems moving at a constant velocity relative to each other."
The second postulate is regarded as a result of Michelson-Morley and other optical experiments and of observations and is believed to represent an experimental fact. It states as: "The velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer."

Thank You

Reference 1: The Michelson-Morley Experiment

2008-08-19T23:51:00.000-07:00

http://www1.umn.edu/ships/updates/m-morley.htm

http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html

Theories of Nuclear Composition

2008-08-11T00:52:00.002-07:00

There are two theories of Nuclear composition. They are as follows:
1.Proton-electron theory of nuclear composition: As electrons are found in β-decay process, and before the discovery of neutrons, it was assumed that nucleus is consisted of protons and electrons.
According to this hypothesis a nucleus of mass no.A and atomic no.Z contains A protons and A-Z electrons. The nucleus is surrounded by Z orbiting electrons so that the atom as a whole is electrically neutral.
But this theory suffers from following limitations:
A> due to the very small size of the nucleus the electrons can notbe considered to
be there.
B> It does not support the observed nuclear spin.
C> Observed magnetic moment of the nucleus does not support the theoreticallly predicted magnetic moment.

2> Proton-Neutron Theory:
After the discovery of neutrons (Chadwick 1932) Proton neutron theory was formulated. According to this theory:
"A nucleus of atomic no. Z and mass no.A consists of Z Protons and (A-Z) neutrons. The no. of extranuclear electrons is Z so that the nuclear charge is balanced."
This theory is able to explain:
* The observed value of nuclear spin and nuclear magnetic moment.
*The existence of isotopes . Isotopes of a given element differ only in the no. of neutrons they contain.
*The β-ray emission of a radioactive element is explained as follows:
The electron does not pre exist in the nucleus.The electron is formed just at the instant of emission, caused by the transformation of a neutron into proton.
i.e. n--->p+e-
*The positron emission is due to the converse process, i.e. when a proton transfers itself into a neutron.
i.e. P--->n+e+
* α and β decay explanation: The emission of α-particles from the nucleus of radioactive elements is due to the combination of 2-protons and 2-neutrons at the instant of emission.
Thus this hypothesis explains α-decay and β-decay.

Let's make our planet livable for our offsprings

Mass defect and Binding energy

2008-08-11T00:07:00.000-07:00

When the Z protons and n neutrons combine to make a nucleus, some of the mass (Δm) disappears, which is converted into an amount of energy given by Einstein's mass-energy relationship;
ΔE=Δmc^2
This amount of energy is called binding energy.
The magnitude of binding energy determines the stability of the nucleus against disintegration. The large the binding energy, more stable the nucleus.
A nucleus having the least possible of binding energy, is said to be in ground state. If the nucleus has energy greater than that of ground state energy (i.e. E >Emin), then it is said to be in excited state.
The case when E=0, this corresponds to the dissociation of the nucleus into it's constituent nucleons.
Let's make our planet livable for our offsprings

Atomic Nucleus

2008-08-10T22:00:00.000-07:00

The atomic nucleus was discovered in 1911by Ernest Rutherford.It is nearly of 10^-14m in diameter and is surrounded by orbiting electrons.
All atomic nuclei are made up of elementary particles called protons and neutrons (however there is no neutron in case of Hydrogen atom). A proton has a positive charge of the same magnitude as that of an electron.a neutron is a chargeless particle with almost the same mass of a proton. the proton and neutron are considered to be two different charge states of the same particle called neucleon.
Nuclear size:The mean radius of an atomic nucleus is of the order of 10^-14 to 10^-15m while that of atom is about 10^-10m. Thus the nucleus is 10000 times smaller in radius than the atom.
Nuclear density: The nuclear density ρ is calculated from:
ρ =Nuclear mass/ nuclear volume
Nuclear density is of the order 10^17 Kg M^-3, which indicates the nuclear matter is in a very compressed state.
Nuclear mass and mass defect: The nucleus consists of protons and neutrons. so the mass of nucleus should be:
assumed nuclear mass =mass of protons+ mass of neutrons,
= ZMp+NMn
Where Z= atomic No.
N= No. of neutrons
Mp=mass of proton
Mn=mass of neutron
However nuclear masses are accurately measured by mass spectrometers, which showed that:
real nuclear mass < ZMp+NMn
This difference in calculated and observed atomic masses is called mass defect,
Mass defect (Δ M)= ZMp + NMn-real ( observed) nuclear mass.

Let's make our planet livable for our offsprings

First Principle of Quantum Mechanics

2008-08-07T23:00:00.000-07:00

An ideal experiment is that one in which there are no uncertain external influence the things going on that we can not takeinto account.In other words an ideal experiment is one in which all the initial and final condition of the experiment are completely specified.
An event is, in general , Just a specific set of initial and final conditions. whenever something is to be happen as a consequence of certain activities it is then said to be an event.
Then we can discuss first principle of quantum mechanics in Richard Feynman's words as :
1> The probability of an event in an ideal experiment is given by the square of the absolute value of a complex number (Φ) which is called the probability amplitude.
P=Φ^2
Where P= Probability
(Φ) =Probability amplitude
2> When an event can occur in several alternative ways, the probability amplitude for the event is the sum of probability amplitudes for each way considered separately. There is interference.
Φ= Φ1+Φ2
P= Φ1+Φ2^2
3> If an experiment is performed which is capable of determining whether one or another alternative is actually taken,the probability of event is the sum of the probabilities for each alternatives. Then the interference is lost.
P= P1+ P2
We will discuss further in coming days. thank you.

Introductory Quantum Mechanics

2008-08-07T21:56:00.000-07:00

We are starting from some ideas about quantum mechanics.
the complete theory of quantum mechanicsdepends on the correctness of the uncertainity principle.Since quantum mechanics is very much successfull theory,our belief in the uncertainity principle is reinforced.But if a way to beat the uncertainity principle were ever discovered, quantum mechanics would give inconsistent results and would have to be discarded.
No one has ever found a way around the uncertainity principle and we have to assume that it describes a basic characteristic of nature.

Let's make our planet livable for our offspring

Hello!

2008-07-31T00:57:00.000-07:00

Hi Everyone
I want to heartly welcome all of you to my blog . We will discuss here the recent ideas about nuclear physics as well as particle and plasma physics here. we will try to understand the phenomenon through the recently developed ideas and techniques .We will also try to find the ways ,that can explain the more complex phenomenon in such a simple way that a simple layman can also discuss them without any hesistation.