Physics Revision: Nuclear Physics

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Alpha Particle

Description:Consists of two protons and two neutrons. Its relative mass is 4 and it has a charge of +2. 

Penetration Power: Stopped by a few cm of air or a thin sheet of paper

Ionisation effect: Very strongly Ionising

Effects of a magnetic field: Weakly Deflected, as its high relative atomic mass means it is very difficult

Although it has a very weak penetrating power, it is still extremely dangerous if it enters the body as its ionisation would kill living cells

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Beta Particle

Description: A high energy electron created and emitted by a nucleus with too many neutrons. 

Electric Charge: -1

Relative Atomic Mass: 1/1860

Penetration Power: Stopped by a few mm of aluminium

Ionisation Effect: Weakly ionising

Effects of Magnetic/Electric Field: Greatly Deflected, as it has a very small mass 

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Gamma Particle

Description: High energy electromagnetic radiation

Electric Charge: 0

Relative Atomic Mass: 0

Penetration Power: Reduced by several cm's of lead or several metres of concrete

Ionisation Effect: Very weakly ionising

Effects of magnetic field: No deflection as there is no mass or charge

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Nuclear Fission

Nuclear fission is the SPLITTING of an atomic nucleus.

The two commonly used fissionable substances are uranium-235 and plutonium-239

For fission to take place these substances must first absorb a neutron

The nucleus splits into two smaller nuclei, releasing 2/3 neutrons and energy. These neutrons strike other nuclei and start a chain reaction. 

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Nuclear Fusion

Nuclear Fusion is the JOINING of two atomic nuclei to form a larger one.

This is the process of how stars release energy.

Stars form when dust and gas are pulled together by gravitational attraction, smaller masses may also form and be attracted by a larger mass to form planets.

During a star's 'main sequence' it is relatively stable as the forces of gravitational attraction and energy released are balanced.

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A Star's Life Cycle

PROTOSTAR>MAIN SEQUENCE STAR

FOR STARS THE SAME SIZE AS THE SUN:

MAIN SEQUENCE STAR>RED GIANT>WHITE DWARF>BLACK DWARF

FOR STARS BIGGER THAN THE SUN:

MAIN SEQUENCE STAR>RED SUPER GIANT>SUPERNOVA>NEUTRON STAR OR BLACK HOLE

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