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 -
---
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.