nuclear physics

TAU101 Applied physical sciences(2+1)

Nuclear Physics

BSF-10001-A.Adhirai002-Alex.K.George003-Aravind.R.S004-K.Bharathidasan005-R.Deepak Kumar


DEFINITION

Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei.

It includes the study of,

1. The general properties of nucleus.

2. The particles contained in the nucleus.

3. The interaction between these particles.

4. Radio activity and nuclear reactions.

5. Practical applications of nuclear phenomena.


NUCLEUSEvery atom contains a

centre, an extremely dense, positively charged nucleus.

The nucleus is made of protons and neutrons.

Protons have positive electric charge.

Neutrons have no electrical charge.



NUCLEUS MASS NUMBER(A): total number of nucleon.A=Z(protons)+N(neutrons).

ATOMIC NUMBER(Z): number of protons.

NEUTRON NUMBER N: number of neutrons.

RADIUS: r=r0A1/3 ,r0=1.25x10-15 m.

MASS M=AU,u=1.66×10⁻27kg

α-RAY SCATTERING EXPERIMENT

Done by E.Rutherford.

From angular distribution of rescattered α -particles Rutherford concluded existence of positively charged core of atom,then called nucleus

The size of the nucleus was much smaller(10-14m) than size of the atom (10-10m)



THE NUCLEAR FORCE

The force that binds together protons and neutrons inside the nucleus is called the Nuclear Force.Some characteristics of the nuclear force are:1.It does not depend on charge.2.It is very short range.3.It is much stronger than the electric force.4.It is saturated force .5.It favours formation of pairs of nucleons with opposite spins.


NUCLEAR BINDING ENERGYThe total rest energy(mass) of the separated nucleons is greater than the rest energy(mass) of the nucleus.Eg:- Deuteron 2H (1 proton + 1 neutron+1 electron)

mp=1.007276u +

mn=1.008665u But m2H=2.014102 u

mp+n=2.016490 u

mp+n-m2H=0.002338u The deuteron is 0.002338 u lighter than the sum of the separate proton and the neutron. This is the binding energy and is the energy needed to break that nucleus apart in its separate constituents

BINDING ENERGY PER NUCLEONNuclei with the

largest binding energy per nucleon are the most stable.

The largest binding energy per nucleon is 8.7 MeV, for mass number A = 56.

Beyond bismuth, A = 209, nuclei are unstable.

Most stableIron 56


RADIOACTIVITYThe Spontaneous emission of radiation by unstable nuclei to become stable. Atain stability by the emission of ,1. α particles( 4He)[atomic number decrease by2 & mass

number decrease by 4]2. β particles (electrons or positrons)[atomic number

change by 1 & mass number remains same]3. γ rays (energetic photons)


HALF LIFE TIME

The half life means time required for the disintegration of half of the sample.Different for different elements.Applied for the estimation of age of fossils(14C-dating).

NUCLEAR REACTIONS

A nuclear reaction is a rearrangement of nuclear components induced by particle bombardment.

1. Fission

2. Fusion Nuclear reactions are subject to the following

conservation laws:

1. Charge.

2. Momentum and angular momentum.

3. Energy.

4. Total number of nucleons.TAU101 Applied physical sciences(2+1)

FISSION Splitting of large nucleus to

smaller ones results in the liberation of energy.

n + 235U →141Ba + 92Kr + 3n In this reaction more than

200MeV energy liberated. Emitted neutrons can induce

addtional fusion-chain reaction. Chain reaction is controlled and

is applied in fission reactors. Chain reaction left uncontrolled

and is applied in atom bomb.TAU101 Applied physical sciences(2+1)

Ba

Kr

FISSION CHAIN REACTION

At each step energy is released !TAU101 Applied physical sciences(2+1)

NUCLEAR FISSION REACTOR

Place where controlled fission chain reaction occurs.Liberated energy is used for the production of

electricity.PARTS OF THE REACTOR;

1. Fuel-Uranium,Plutonium,Thorium

2. Moderator-Water,Graphite-slow down neutron.

3. Control rods-Cadmium-absorb neutrons.

4. Concrete wall-block radiations.

emitted in fission are more energetic so they need to be slowed down

by means of a moderator (water, graphite) placed in between the fuel

rods. Control rods, of Cadmium or other materials, are further used to

regulate the number of fission inducing neutrons


NUCLEAR FISSION REACTOR


FUSION


Two light nuclei fuse together to form a heavier nucleus results in the liberation of energy. 2H + 3H →4He + n + 17.6 MeVIt is the primary source of the sun’s energy.Fusion reaction is applied in hydrogen bomb.

FISSION & FUSIONFUSIONFISSION


FISSION & FUSIONFISSION

Splitting a large mass nucleus into two medium mass nucleus.

Energy released per nucleon is less.

Can be controlled. Heat is not needed. Lot radioactive

byproducts.

FUSION Joining two low mass

nuclei into a larger mass nucleus.

Energy produced per nucleon is large.

Can not be controlled.

Extreme heat is needed.

No radioactive byproducts.



NUCLEAR REACTORSFISSION REACTOR:use fission of heavy elementslike Uranium, Plutonium for power.

FUSION REACTOR:work in progress: ITERInternational Thermonuclear Experimental Reactor(500MW power in 1000second through fusion reaction)


APPLICATIONS ARE

Medical radio-isotopes (imaging & therapy).Magnetic Resonance Imaging (MRI).Identification of materials.Dating of materials.Power generation (fusion and fission).Weapons of mass destruction (WMD).

REFERENCE

NCERT physics text book. www.elsevier.com. www.sciencedirect.com. www.wikipedia.org.


nuclear physics

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