Alpha, Beta, and Gamma Radiation: Properties and Characteristics
Nature of Radiation
Introduction: When an unstable nucleus decays, it releases energy and matter to become more stable. These emissions are categorized by their charge, mass, and penetrating power. Understanding the differences between Alpha (\(\alpha\)), Beta (\(\beta\)), and Gamma (\(\gamma\)) radiation is fundamental to safety and nuclear physics.
1. Properties of the Emissions
Radioactive emissions originate from the nucleus. The table below summarizes their key properties based on the CSEC syllabus.
| Property | Alpha (\(\alpha\)) | Beta (\(\beta\)) | Gamma (\(\gamma\)) |
|---|---|---|---|
| Symbol | \( ^4_2\text{He} \) or \( \alpha \) | \( ^0_{-1}\text{e} \) or \( \beta^- \) | \( \gamma \) |
| Nature | Helium Nucleus (2p + 2n) | High-speed Electron | Electromagnetic Wave |
| Charge | +2e | -1e | 0 (Neutral) |
| Mass | 4 amu (Heavy) | 1/1836 amu (Very Light) | 0 (Massless) |
| Ionizing Ability | High (Strongest) | Moderate | Low (Weakest) |
| Penetrating Power | Low (Stopped by paper/skin) | Moderate (Stopped by Aluminum ~5mm) | High (Reduced by thick Lead) |
| Speed | ~5% speed of light | ~90% speed of light | Speed of light |
2. Interactive Lab: Penetration & Absorption
🛡️ The Absorption Experiment
Objective: Fire different types of radiation at barriers of increasing density. Observe which particles pass through and which are absorbed.
3. Deflection in Magnetic Fields
Charged particles moving through a magnetic field experience a force (the Lorentz Force). This force is perpendicular to both the velocity of the particle and the magnetic field direction.
Alpha (\(\alpha\)) Deflection
Charge: +2. Mass: Heavy.
It is deflected in one direction. However, because it is heavy, its radius of curvature is large (it turns slowly).
Beta (\(\beta\)) Deflection
Charge: -1. Mass: Very Light.
It is deflected in the opposite direction to Alpha. Because it is so light, it deflects very sharply (tight curve/spiral).
Gamma (\(\gamma\))
Charge: 0.
Since it has no charge, Gamma rays are not deflected by magnetic or electric fields. They travel in a straight line.
🧲 Magnetic Field Simulation
Imagine the magnetic field lines are going INTO the screen (represented by the X's).
Wait a moment for particles to be emitted automatically.
4. Cloud Chamber Tracks
A cloud chamber makes the paths of radiation visible by condensing vapor on the ions left behind by the radiation.
Alpha Tracks
Thick and Straight.
Because Alpha particles are highly ionizing, they knock many electrons off atoms, creating dense tracks. They are also heavy, so they don't scatter easily.
Beta Tracks
Thin and Wiggly/Scattered.
Beta particles are less ionizing (thinner tracks) and very light, so they bounce off atoms easily, causing jagged paths.
Gamma Tracks
None usually visible.
Gamma rays have very low ionizing power, so they rarely produce visible tracks in a standard cloud chamber.
CSEC Practice Questions
Test Your Knowledge
1. Which radiation is stopped by a sheet of paper?
2. In a magnetic field perpendicular to their motion, Beta particles are deflected much more than Alpha particles because:
3. Which of the following has the highest ionizing ability?
🎯 Exam Tip: Safety
When asked about safety precautions for handling radioactive sources:
- Time: Minimize exposure time.
- Distance: Keep as far away as possible (use tongs).
- Shielding: Use appropriate absorbers (Lead box for Gamma).