Types of Radiation | Physics for GCSE/IGCSE - Year 11 PDF Download

Radioactive Decay

• Some atomic nuclei are unstable
• Unstable nuclei result from imbalances in forces within the nucleus. These forces exist between particles in the nucleus and are often due to an excess of protons or neutrons.
• The presence of excess protons or neutrons within the nucleus leads to the imbalance of forces between particles.
• Carbon-14, an isotope of carbon, exemplifies instability with two extra neutrons compared to stable carbon-12.
  
  Carbon-12 is stable, whereas carbon-14 is unstable. This is because carbon-14 has two extra neutrons
• Certain isotopes become unstable due to their significant size or an imbalance in the number of neutrons.
• To achieve stability, unstable nuclei emit radiation.
  • This radiation can manifest as either high-energy particles or waves.

Unstable nuclei decay by emitting high energy particles or waves

• As radiation disperses from the nucleus, it carries away some energy, diminishing the nucleus's overall energy and rendering it more stable.
• This process, known as radioactive decay, is random in nature, making it impossible to precisely predict when a specific nucleus will decay.
• The unpredictability arises because any nucleus has an equal likelihood of decaying, and the timing of decay cannot be determined.
• Furthermore, the rate of decay remains constant regardless of external conditions, making it only possible to estimate the probability of nuclei decaying within a given timeframe.
• Consequently, the emission of radiation is spontaneous, occurring randomly in direction.

Types of Radioactive Decay

• Radioactive decay occurs when an unstable nucleus emits nuclear radiation.
• There are three main types of radiation that can be emitted:
  • Alpha (α) particles
  • Beta (β-) particles
  • Gamma (γ) radiation
• These changes are spontaneous and random

Alpha Particles

• Alpha particles, represented by the symbol α, are identical to helium nuclei.
• Comprising two neutrons and two protons, they possess a charge of +2 and thus can be influenced by an electric field.

Beta Particles

• Beta particles, symbolized by β, are fast-moving electrons.
• They are generated in nuclei when a neutron decays into a proton and an electron.
• Beta particles carry a charge of -1, making them responsive to electric fields.

Gamma Rays

• Gamma rays, represented by γ, are electromagnetic waves.
• They possess the highest energy among various electromagnetic waves.
• Gamma rays are uncharged.

Alpha particles, beta particles and gamma waves can be emitted from unstable nuclei

Alpha, Beta & Gamma Emission

•  Nature:  Alpha, beta, and gamma radiation can be distinguished by understanding the type of particle or radiation they are.
•  Relative Ionising Effects:  This refers to how easily these radiation types can ionize other atoms.
•  Relative Penetrating Abilities:  It indicates how far alpha, beta, and gamma radiation can travel before being completely stopped.
• The properties of Alpha, Beta and Gamma:  These properties are presented in a table and further elaborated below.

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

Penetrating Power

• Alpha, beta, and gamma radiation possess distinct properties.
• They penetrate materials differently, affecting the materials they interact with.
  • Alpha radiation has the least penetrating power, while gamma radiation is the most penetrating.

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

• Alpha radiation is effectively stopped by paper, whereas beta and gamma rays can pass through it.
• Beta radiation requires only a few millimeters of aluminum to be stopped, while gamma rays can penetrate aluminum.
• Gamma rays are only partially obstructed by thick lead.