E.3.10—Radiation penetration and ionization
- Syllabus
- First assessment 2025
- Objective
- —
- Level
- SL
Compare Radiation Types
Alpha radiation
Alpha particles are heavy and doubly charged. They interact strongly with matter, so they are highly ionizing but have low penetration and a short range in air.
Beta radiation
Beta particles are much lighter and singly charged. They are moderately ionizing and more penetrating than alpha particles, but can be deflected by electric and magnetic fields.
Gamma radiation
Gamma photons are neutral and travel at the speed of light in vacuum. They are weakly ionizing compared with alpha and beta, but have the greatest penetration.
Common trap
Do not rank penetration and ionization in the same order. The usual qualitative order is alpha > beta > gamma for ionization and gamma > beta > alpha for penetration.
E.3.10 Exam Analysis
Assessment in practice
1–2 marksHow it is assessed
Questions compare gamma speed, penetration and ionization or explain why beta travels further than alpha at equal kinetic energy.
Command terms
Compare / Outline
What earns marks
Use charge, mass and interaction strength to justify the qualitative ranking, not just memorize it.
Watch for
Claiming gamma is more ionizing than beta or ignoring the different charge and mass when comparing ranges.