Properties of Alpha, Beta & Gamma (OCR Gateway GCSE Physics)

Properties of Alpha, Beta and Gamma Radiation

• The properties of Alpha, Beta and Gamma are given in this table, and then described in more detail below

Different Properties of Nuclear Radiation

• The trend down the table shows:
  • The range increases
  • Penetrating power increases
  • Ionisation decreases

Penetrating Power

• Alpha, beta and gamma have different properties
• They penetrate materials in different ways
  • This means they are stopped by different materials

Alpha, beta and gamma are different in how they penetrate materials. Alpha is the least penetrating, and gamma is the most penetrating

• Alpha is stopped by paper
  • Beta and gamma can pass through paper
• Beta is stopped by a few millimetres of aluminium
  • Gamma can pass through aluminium

• Gamma rays are only partially stopped by thick lead
  • Nothing can completely stop gamma radiation

Ionising Power

• All nuclear radiation is capable of ionising atoms that it hits
• When an atom is ionised, the number of electrons it has changes
• This gives it a non-zero charge

When radiation passes close to atoms it can knock out electrons, ionising the atom

• Alpha radiation is the most ionising form of nuclear radiation
  • This is because alpha particles have a charge of +2

• Gamma radiation is the least ionising form of nuclear radiation

Range in Air

• The more ionising a form of radiation is, the sooner it will react with the air it is moving through
• Strongly ionising radiation has the shortest range in air
  • Alpha only travels a few centimetres in air
  • Beta has a range of a few tens of centimetres
  • Gamma is not absorbed by air and so has an infinite range, although it does get less intense with distance

ANSWER:  B

• • The answer is not A because the radiation passed through the paper almost unchanged
    • This means it is not alpha

  • The answer is not C or D because the aluminium decreased the count-rate significantly
    • This means it is not gamma (gamma penetrates aluminium)
    • This also means it is not neutrons (neutrons penetrate aluminium, however you do not need to know this for your GCSE)

  • Therefore, the source must be beta particles