What is Radiation?

Health Physics Society - Power Reactor Section

Radiation Science Education

Outline

• Ionizing & Non-Ionizing

• Photons & Particles

• Stable & Unstable Atoms

• Half -Life

• Radiation Detectors

Ionizing & Non-Ionizing Radiation

Ionizing Radiation: Radiation is energy transmitted as particles or waves. Ionizing radiation has sufficient energy to dislodge orbital electrons, thereby producing ions.

Examples: alpha, beta, gamma, neutron, and x-rays

Non-Ionizing Radiation: Radiation that does not have sufficient energy to dislodge orbital electrons.

Examples: visible light, infra-red , micro-waves, radio-waves,

and radar

Ionizing Radiation Hits An Atom

Incoming

Photon

EjectedElectro

n

Particles and Photons

• Radiation can be in the form of particles or waves (photons).

• The most common types of ionizing radiation are alpha, beta, gamma, neutron, and x-rays.

– Gamma and x-ray radiation are photons. They are part of the electromagnetic spectrum and considered packets of pure energy.

– Alpha, beta, and neutron radiation are particles having mass. Betas are electrons and alphas are helium nuclei.

Electromagnetic Spectrum

Radioactive Decay: The process of unstable atoms spontaneously emitting radiation.

Half-Life = 1.3 billion years

Parent NucleusPotassium-40Unstable atom

Daughter NucleusCalcium-40Stable atom

What is Half-Life?

• Radioactive decay is the process where an unstable atom emits radiation.

• Radioactive decay changes unstable atoms into more stable atoms.

• Half-life is the time it takes for 1/2 the atoms of a particular radioactive element to transform itself by decay.

Gas-Filled Detectors

Incident Ionizing

Radiation +++

Anode +

Voltage Source

ElectricalCurrent

Measuring Device

Cathode -

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Key Concepts

Radioactive Decay: The process where an unstable atom transforms itself into a more stable atom by spontaneous emission of radiation.

Ionizing Radiation: Any radiation which is capable of dislodging electrons from atoms thereby producing ions.

Half Life: The time it takes for one-half of the atoms of a particular radioactive element to transform itself by radioactive decay.