Nuclear Physics

and Beyond

Blue Excelsiors

Lessons To Be TackledI – Atomic StructureII – The Strong Nuclear ForceIII – Radioactivity

-Alpha Decay – Beta decay –Gamma Decay

IV - StabilityV – Half-lifeVI – ActivityVII – Mass defect and Binding EnergyVIII – Nuclear Fission

-Nuclear Reactors

IX – FusionX – Beneficial Uses of Radiation

-Medical Uses -Non-Medical UsesXI – Biological Effects of RadiationXII – Radiation Detection and ProtectionXIII – Interaction of Matter with RadiationXIV – Special Relativity

-Time Dilation -Length Contraction-Mass Increase Mass-Energy

EquivalenceXX – Elementary Particles

-Quarks -Leptons-Field Particles

I – The Atomic Structure

-An atom may be viewed like a mini solar system. It is composed of negatively charged particles called

electrons orbiting around a positively charged

particles called neutrons.

II – The Strong Nuclear Force

-A force that exists to counteract the force of repulsion between the protons in the nucleaus

The strong nuclear force is very important in attaining stability for the nucleus. For a nucleus to be stable it has to have a balance between protons and the force of attraction between nucleons by the strong nuclear force.

III – Radioactivity

-The heat transfers by electromagnetic waves.

The types of radiation-Alpha Decay-Beta Decay-Gamma Decay

Alpha Decay-An alpha particle consist of a positively charged nucleus of the helium atom. It has a charge of +2e and a mass number of 4.

Beta Decay -There are three forms of Beta

Decay:*beta-minus *beta-plus

*electron captureThe atomic number of the parent

nucleus increases by 1, while the mass number remains the same.

Gamma Decay-Gamma Decay involves the release of high-energy electomagnetic waves called gamma rays (y). This happens when nucleus changes from an excited or high energy state to a lower energy state. In the result, there is no change in the atomic number as well as in the mass number of the parent atom.

IV - Stability

IV – Half-Life

-The half-life T1/2 of a radioactive material is the time required for half of the nuclei present to disintegrate. After the first half-time, one-half of the radioactive materials would have disintegrated and one-half remains unchanged. After another half-life, the remaining one-half nuclei disintegrate, and so on.

VI - Activity

-Activity is the number of disintegrations or decays per unit time. Its SI unit is the Becquerel, abbreviated as Bq.

1 Bq = 1 disintegration/second

VII – Mass Defect and Blinding Energy

-Mass Defect and Binding Energy Summary Mass defect is the difference between the mass of the atom and the sum of the masses of its constituent parts.

-Binding energy is the amount of energy that must be supplied to a nucleus to completely separate its nuclear particles. Binding energy is the energy equivalent of the mass defect.

-Binding energy can be calculated by multiplying the mass defect by the factor of 931.5 MeV per amu.

VIII & IX– Nuclear Fission and Fusion

Two important nuclear reactions will be considered here. These are fission and fusion. Bother reactions release a large amount of energy because the sum of the masses of the product nuclei is less than the sum of the masses of the product nuclei is less than the sum of the masses of the initial nuclei. Once again, Einstein’s equation, E=mc2, explains that this mass defect is converetd into energy.

Fission-Is the process in which a large nucleus

breaks into two smaller nuclei accompanied by emission of neutrons and a large amount of energy.

Fusion-Is the process in which small nuclei

combine form larger nuclei.

Nuclear ReactorsSimply a furnace where energy is generated by

controlled fission chain reaction of the fuel.Essential Parts of a Nuclear Reactor

a) Fuel – The fuel is placed in metal tubes and placed close to on another

b) Moderator – Neutrons produced by the nuclear fission reaction have high energy and are slowed down by a moderator. One common moderator is water.

c) Control rods – Are normally made of boron or cadmium and have the ability to absorb neutrons without fission taking place.

d) Coolant – Usually water is used to move the heat away from the fission reactor. Coolant may also acts as moderator.

e) Inner Containment Structure or Shielding – The shielding helps prevent radiation leakage.

X – Beneficial Uses of Radiation

Non-Medical UsesIncludes cobalt-60 used to preserve food by killing viruses or bacteria that hasten decay. -Radioisotope thermonuclear generator use to power up 24 U.S. spacecrafts.

And others for metal shaping, locating leak on pipes, smoke detecting, detecting explosives, and measuring dust and pollutant levels.

XI – Biological Effects of Radiation