Seneca
Sign up

Alpha & Beta Radiation

Physics: AQA A Level, topic 8.1.2

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 60.
  • 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 aluminium or about 30 cm of air.
  • A beta source is used for gauging the thickness of aluminium sheeting or foil.
  • A beta-plus emitter is used in medical PET scanning.

Radioactivity Safety

All institutions that hold radioactive sources need a permit to do so. The institution will have to follow some local rules about storage and use of sources. Protective measures should include:

Protective clothing

Protective clothing

  • Wearing goggles and gloves.
Pointing sources away

Pointing sources away

  • Sources should be pointed away from people including yourself.
Keeping the source at arm's length

Keeping the source at arm's length

  • Tongs should be used when moving the source.
Reducing exposure time

Reducing exposure time

  • Put the source away when it’s not in use so as to reduce exposure time.
Protective box

Protective box

  • Keep the source in a lead-lined box.

Test yourself on Alpha & Beta Radiation

  • What are alpha particles made of?

  • Which of these are appropriate safety measures when handling radioactive sources?

  • Which of these will not protect someone from beta radiation?

Practise this topic for free