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Radioactive Decay and Nuclear Radiation
Radioactive Decay
- Some atomic nuclei are STABLE and some are UNSTABLE.
- RADIOACTIVE DECAY is a process where UNSTABLE atomic nuclei release RADIATION to become more STABLE. It is a RANDOM PROCESS.
- The ACTIVITY of a radioactive substance is the rate at which it decays, and it is measured in BECQUERELS (Bq). One Becquerel equals one decay per second.
- COUNT-RATE refers to the number of decays detected per second. It is measured with an instrument known as a GEIGER-MULLER TUBE.
Types of Nuclear Radiation
Alpha Particles (α)
- ALPHA PARTICLES are made up of two neutrons and two protons, making them identical to a helium nucleus.
- They have a LOW penetration ability and can be stopped by just a sheet of paper. This is due to their large size compared to other forms of radiation.
- They are STRONGLY IONISING because they can knock out electrons from atoms, turning them into ions quite effectively.
Beta Particles (β)
- A BETA PARTICLE is a high-speed electron ejected from a nucleus. Despite having a small mass, they carry a single negative charge.
- They are MODERATELY IONISING and have a greater penetrating power than alpha particles, traveling several metres in air and can be absorbed by materials such as aluminium about 5mm thick.
- When a beta particle is emitted, a NEUTRON in the nucleus is turned into a PROTON.
Gamma Rays (γ)
- GAMMA RAYS are a type of ELECTROMAGNETIC RADIATION with no mass and no charge, enabling them to penetrate materials much more effectively than alpha or beta particles.
- They have the LOWEST ionising power but can travel the LONGEST distances through air and materials.
- To STOP gamma rays, you need thick sheets of dense materials like lead or several metres of concrete.
Uses of Radiation
The different types of radiation have various uses due to their properties:
Alpha Radiation in Smoke Detectors:
- Alpha radiation is suitable for SMOKE DETECTORS because alpha particles have a high ionising ability, which means they can ionize air particles very effectively, creating a detectable electric current. The relatively large size of alpha particles makes them interact strongly with matter, such as smoke particles. When smoke interrupts the flow of ions, the current drops, which the detector senses and thus sets off the alarm. This sensitivity to changes in air composition is crucial for the early detection of fires.
Beta Particles in Material Thickness Measurement:
- The use of beta particles for gauging material THICKNESS is advantageous because beta particles have a moderate penetration depth and ionising power. They are absorbed at predictable rates by different materials, allowing for precise thickness measurements. Beta particles can penetrate materials enough to provide information without passing completely through, which is ideal for non-destructive testing of materials like sheets of metal.
Gamma Rays as Medical Tracers:
- Medical tracers are injected into the body, and flow through the blood where the radiation can be detected externally to follow its progress around the body.
- Gamma rays are well-suited as MEDICAL TRACERS due to their ability to penetrate tissues and exit the body without being absorbed as much as alpha or beta radiation. This allows them to be detected by external sensors after being emitted by a source inside the patient, providing valuable images. Their lower ionising power compared to alpha particles reduces the risk of damage to healthy tissues during their use in medical imaging.
Radioactive Decay and Nuclear Radiation
Radioactive Decay
- Some atomic nuclei are STABLE and some are UNSTABLE.
- RADIOACTIVE DECAY is a process where UNSTABLE atomic nuclei release RADIATION to become more STABLE. It is a RANDOM PROCESS.
- The ACTIVITY of a radioactive substance is the rate at which it decays, and it is measured in BECQUERELS (Bq). One Becquerel equals one decay per second.
- COUNT-RATE refers to the number of decays detected per second. It is measured with an instrument known as a GEIGER-MULLER TUBE.
Types of Nuclear Radiation
Alpha Particles (α)
- ALPHA PARTICLES are made up of two neutrons and two protons, making them identical to a helium nucleus.
- They have a LOW penetration ability and can be stopped by just a sheet of paper. This is due to their large size compared to other forms of radiation.
- They are STRONGLY IONISING because they can knock out electrons from atoms, turning them into ions quite effectively.
Beta Particles (β)
- A BETA PARTICLE is a high-speed electron ejected from a nucleus. Despite having a small mass, they carry a single negative charge.
- They are MODERATELY IONISING and have a greater penetrating power than alpha particles, traveling several metres in air and can be absorbed by materials such as aluminium about 5mm thick.
- When a beta particle is emitted, a NEUTRON in the nucleus is turned into a PROTON.
Gamma Rays (γ)
- GAMMA RAYS are a type of ELECTROMAGNETIC RADIATION with no mass and no charge, enabling them to penetrate materials much more effectively than alpha or beta particles.
- They have the LOWEST ionising power but can travel the LONGEST distances through air and materials.
- To STOP gamma rays, you need thick sheets of dense materials like lead or several metres of concrete.
Uses of Radiation
The different types of radiation have various uses due to their properties:
Alpha Radiation in Smoke Detectors:
- Alpha radiation is suitable for SMOKE DETECTORS because alpha particles have a high ionising ability, which means they can ionize air particles very effectively, creating a detectable electric current. The relatively large size of alpha particles makes them interact strongly with matter, such as smoke particles. When smoke interrupts the flow of ions, the current drops, which the detector senses and thus sets off the alarm. This sensitivity to changes in air composition is crucial for the early detection of fires.
Beta Particles in Material Thickness Measurement:
- The use of beta particles for gauging material THICKNESS is advantageous because beta particles have a moderate penetration depth and ionising power. They are absorbed at predictable rates by different materials, allowing for precise thickness measurements. Beta particles can penetrate materials enough to provide information without passing completely through, which is ideal for non-destructive testing of materials like sheets of metal.
Gamma Rays as Medical Tracers:
- Medical tracers are injected into the body, and flow through the blood where the radiation can be detected externally to follow its progress around the body.
- Gamma rays are well-suited as MEDICAL TRACERS due to their ability to penetrate tissues and exit the body without being absorbed as much as alpha or beta radiation. This allows them to be detected by external sensors after being emitted by a source inside the patient, providing valuable images. Their lower ionising power compared to alpha particles reduces the risk of damage to healthy tissues during their use in medical imaging.
