Ionising Power & Deflection | Physics for GCSE/IGCSE - Year 11 PDF Download

Ionising Effect of Radiation

• Ionization occurs when an atom acquires a negative or positive charge through the gain or loss of electrons.
• All forms of nuclear radiation possess the ability to ionize atoms upon impact.
• Ionization alters the electron count within an atom, typically achieved by dislodging an electron, resulting in the atom's conversion to a positive charge.

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

Alpha Particles

• Alpha particles leave a dense trail of ions affecting atoms they encounter.
• They quickly lose energy due to their short range.
• When handled carefully, their short range makes them relatively harmless but can be dangerous if the emitter enters the body.

Beta Particles

• Beta particles are moderately ionizing with a longer range than alpha.
• They are more dangerous than alpha as they can penetrate the skin and cause significant damage.

Gamma Radiation

• Gamma rays are the least ionizing but still hazardous.
• They are highly penetrating with a greater range compared to alpha or beta radiation.
• Large amounts of gamma radiation can be hazardous.

Ionizing Effects of Radiation

• Gamma rays, due to their lower ion production compared to alpha and beta radiation, possess increased penetration abilities and a wider range, rendering them potentially hazardous in significant quantities.
• This increased penetration capability of gamma rays is attributed to their reduced ion production.
• The ionizing effects of radiation are contingent upon the kinetic energy and charge associated with the specific type of radiation.

Charge Influence on Ionization

• The level of ionization is directly correlated with the charge carried by the radiation. Alpha radiation demonstrates the highest ionization potential with a charge of +2. In contrast, beta radiation, with a charge of -1, exhibits moderate ionization. Gamma radiation, with a neutral charge of 0, is the least ionizing.
• Alpha radiation, characterized by a charge of +2, stands out as the most ionizing form.
• Beta particles, with a charge of -1, display a moderate level of ionization.
• Gamma radiation, devoid of charge (0), represents the least ionizing form among the three.

The Ionising Power of Radiation

• The Effect of Kinetic Energy on Ionising Power:
  • Higher kinetic energy results in increased ionising power.
  • Alpha Particles:
    • Alpha particles are highly ionising due to their large mass.
  • Beta Particles:
    • Beta particles, being light (electrons) and fast-moving, possess moderate ionising power.
  • Gamma Radiation:
    • Gamma radiation, having no mass, exhibits weak ionising power.
• Understanding Ionising Power through Particle Properties:
  • Alpha Particle Properties:
    • An alpha particle is a helium nucleus composed of two protons and two neutrons.
    • It carries a charge of +2 (each proton having a charge of +1).

Deflection in Electric & Magnetic Fields

• A particle experiences deflection in an electric field if it possesses a charge.
• In a magnetic field, a particle is deflected if it has a charge and moves perpendicular to the field.
  • As gamma (γ) particles lack charge, they remain unaffected by both electric and magnetic fields.
  • Only alpha (α) and beta (β) particles undergo deflection in such fields.

Electric Fields

• Alpha particles carry a charge of +2, akin to a helium nucleus.
• Beta particles possess a charge of -1, resembling an electron's charge.
• Hence, in an electric field formed between negatively and positively charged plates:
  • Alpha particles veer towards the negative plate.
  • Beta particles veer towards the positive plate.
  • Gamma radiation remains unimpeded, traveling directly between the plates.

• Beta particles are lighter than alpha particles.
  • Consequently, beta particles experience greater deflection in the electric field, while alpha particles encounter less deflection.

Magnetic Fields

• Likewise, when alpha and beta particles are in motion, they experience deflection in magnetic fields.
• Their deflection occurs in opposite directions owing to their opposing charges.