Alpha vs Beta vs Gamma Radiation

Alpha Radiation

A helium-4 nucleus (2 protons + 2 neutrons) ejected by heavy unstable nuclei. Heavy and doubly charged, so it ionizes intensely but is stopped by a sheet of paper or skin.

${}^{4}_{2}\mathrm{He}$

Unit: particle

Example: Americium-241 in smoke detectors emits alpha particles — safely contained inside the device, they ionize air to detect smoke.

Beta and Gamma Radiation

Beta radiation is a fast electron (or positron) from neutron decay; gamma radiation is a high-energy photon from an excited nucleus. Beta penetrates further than alpha; gamma penetrates far through matter.

$\beta: e^-,\quad \gamma: E = hf$

Unit: particle / photon

Example: Beta from carbon-14 is stopped by aluminum foil; gamma from cobalt-60 needs centimeters of lead or meters of concrete to be absorbed.

Key differences

Aspect	Alpha Radiation	Beta and Gamma Radiation
What it is	Helium nucleus (2p + 2n)	Beta: electron/positron · Gamma: high-energy photon
Charge	+2e	Beta: −e or +e · Gamma: 0
Mass	Heavy (~7300× electron mass)	Beta: light · Gamma: massless
Ionizing power	Very high — dense damage track	Beta: moderate · Gamma: low per photon
Penetration	Centimeters of air; stopped by paper	Beta: meters of air, mm of aluminum · Gamma: needs lead/concrete
Main hazard	Dangerous if inhaled or ingested	External exposure hazard; shielding matters

Why students confuse them

'Radiation' is not one thing. Alpha can't reach you through skin but is devastating inside the lungs; gamma barely notices skin but passes through the body. Protection depends entirely on which type you're dealing with.