What is radioactivity?

The emission of visible light when atoms are heated The spontaneous emission of particles or electromagnetic radiation from an unstable atomic nucleus The absorption of energy by electrons jumping to higher shells The release of electrons when a material is exposed to ultraviolet light

What is emitted in alpha (α) decay?

An electron from the nucleus A high-energy photon A helium nucleus consisting of 2 protons and 2 neutrons (charge +2) A neutron from the outer part of the nucleus

What happens during beta-minus (β⁻) decay?

A proton converts to a neutron, emitting a positron A neutron in the nucleus converts to a proton, emitting an electron (the beta particle) and an antineutrino The nucleus emits a helium nucleus and gains 2 protons An electron from an outer shell falls into the nucleus and annihilates a proton

What is gamma (γ) radiation?

A stream of high-speed electrons emitted from the nucleus A type of alpha particle with extra energy High-energy electromagnetic radiation (photons) emitted when an excited nucleus releases excess energy after an alpha or beta decay Protons emitted at high speed from heavy nuclei

Which type of radiation is the most penetrating, and which is the most ionising?

Alpha is most penetrating; gamma is most ionising Gamma is most penetrating (requires lead/concrete); alpha is most ionising (dense, doubly charged — causes maximum ionisation per unit path) Beta is both most penetrating and most ionising All three types are equally penetrating and equally ionising

Why does radiation pose a health risk to living things?

Radiation heats up cells until they boil and die Ionising radiation removes electrons from atoms in body cells, which can break chemical bonds — including DNA — leading to mutations and cancer Radiation magnetises iron in the blood, disrupting circulation Radiation causes atoms to gain mass, making cells too heavy to function

Gamma radiation is used in cancer radiotherapy. How does it kill cancer cells?

Gamma radiation heats the tumour directly until it evaporates Gamma radiation pushes cancer cells to the surface of the body where they can be removed High-energy gamma photons ionise atoms in the cancer cells, damaging DNA so severely that the cells cannot replicate and die Gamma radiation magnetises cancer cells so the immune system can find and destroy them

Household smoke detectors often contain a tiny amount of americium-241, an alpha emitter. How does this detect smoke?

Alpha particles react chemically with smoke to produce a visible glow that triggers a light sensor Alpha particles ionise air in a small chamber, creating a tiny current; smoke particles disrupt this current — the drop in current triggers the alarm Americium-241 produces heat that melts a wax seal — smoke speeds this up and triggers the alarm Alpha radiation heats smoke particles until they glow, activating a heat sensor

What precautions should be taken when working with radioactive sources in a laboratory?

Always hold sources close to the body to get readings quickly Wear rubber gloves — these stop all forms of radiation Keep sources at a distance (using tongs), minimise exposure time, use appropriate shielding (lead for gamma, aluminium for beta, paper for alpha), never ingest or inhale sources Radiation only causes harm after very long exposures — short lab sessions need no precautions

PET (Positron Emission Tomography) scans use radioactive tracers that emit positrons (β⁺). How does this create an image of the body?

Positrons are fluorescent — they glow inside the body and cameras capture the image Each emitted positron immediately annihilates with a nearby electron, producing two gamma photons in opposite directions — detectors surrounding the patient locate the source Positrons travel through the body and exit the skin where detectors count them The radioactive tracer is attracted to tumours by magnetic resonance