Home / Topics / Atomic & Nuclear Physics
Interaction of radiation with matter
Advanced
Alpha, beta and gamma penetrate differently.
Alpha: strongly ionising, range of cm in air. Beta: penetrates mm of aluminium. Gamma: attenuated exponentially I = I₀e^{−μx}, needing lead or concrete.
Half-value thickness of lead for 1 MeV gamma ≈ 1 cm.
Neutrons need hydrogen-rich shields.
In more detail
Radiation interacts with matter through ionisation, excitation and nuclear reactions. Alpha particles lose energy quickly, while gamma rays penetrate deeply and require dense shielding.
Real-world uses
- Radiation shielding is designed based on these interactions.
- Medical radiation treatments use controlled interactions with tissue.
- Radiation protection engineers choose shielding according to whether the radiation is alpha, beta or gamma.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Why are alpha particles stopped easily?
They are heavy and charged, so they ionise strongly and lose energy quickly.
Why do gamma rays penetrate?
They are uncharged and interact weakly, so they travel far before being absorbed.
Which radiation is hardest to stop?
Gamma rays are the most penetrating and need thick shields of lead or concrete.
Related topics in Atomic & Nuclear Physics
Neutron discovery · Neutrinos · Radiation detection · Radiation units · Biological effects of radiation · Medical uses of radiation