5.1.5

Alpha, Beta & Gamma Radiation

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Alpha (α) Radiation

Unstable nuclei emit one of three types of radiation: alpha, beta and gamma.

Properties of α radiation

Properties of α radiation

  • Alpha particles are:
    • Two protons and two neutrons bound together (the equivalent of a helium nucleus).
    • Weakly penetrating.
    • Easily absorbed.
    • Positively charged.
Properties of α radiation 2

Properties of α radiation 2

  • Alpha particles can only be emitted by nuclei with an atomic number greater than 82.
  • Typically, alpha particles cannot penetrate through a sheet of paper or a few mm of air.
Applications of α radiation

Applications of α radiation

  • An alpha source is used in fire alarms.
    • Alpha particles cannot penetrate through smoke. This is detected and sets off the alarm.

Beta Radiation

Unstable nuclei emit one of three types of radiation: alpha, beta and gamma.

Properties of β radiation

Properties of β radiation

  • Beta particles are:
    • Electrons (or positrons) that are emitted from an unstable nucleus.
    • Moderately penetrative.
    • Either positively or negatively charged.
    • Beta plus particles emitted by proton-rich nuclei.
    • Beta minus particles emitted by neutron rich nuclei.
Applications of beta particles

Applications of beta particles

  • Typically, beta particles cannot penetrate through about 5 mm of aluminum or about 30 cm of air.
  • A beta source is used for gauging the thickness of aluminum sheeting or foil.
  • A beta-plus emitter is used in medical PET scanning.

Gamma Radiation

Unstable nuclei emit one of three types of radiation. alpha, beta and gamma.

Properties of γ radiation

Properties of γ radiation

  • Gamma radiation:
    • Does not change the proton or nucleon number of a nucleus.
    • Makes the nucleus more stable by its emission.
    • Is highly penetrative.
    • Can be absorbed by several centimetres of lead, many metres of air and can travel through a vacuum indefinitely.
Properties of γ radiation 2

Properties of γ radiation 2

  • Gamma radiation is part of the electromagnetic spectrum.
  • Gamma radiation follows an inverse square law:
    • intensity at distance x from the source =constantx2= \frac{constant}{x^2}
Applications

Applications

  • Gamma radiation is used extensively in medical imaging, curing cancer by destroying tumorous cells and for sterilizing medical equipment.
  • It can be used to irradiate food to stop food from going bad.
Jump to other topics
1

Space, Time & Motion

2

The Particulate Nature of Matter

3

Wave Behaviour

4

Fields

4.1

Circular Motion

4.2

Newton's Law of Gravitation

4.3

Fields

4.4

Fields at Work

4.5

Electric Fields

4.6

Magnetic Effect of Electric Currents

4.7

Heating Effect of Currents

4.8

Electromagnetic Induction

4.9

Power Generation & Transmission

4.10

Capacitance

5

Nuclear & Quantum Physics

6

Measurements

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    Alpha particles are:Fill in the list
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    Beta particles are:Fill in the list
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