Prelims - Basic Concepts of Radiation

Radiation

Radiation

Emission of energy by atoms and transition of this energy through space. It consists of a flow of atomic and subatomic particles and waves, such as those that characterized heat.

Natural background sources

Sources of Radiation Exposure where people are constantly exposed to small amounts of; Our bodies have adapted to it.

Man-made or artificial sources

Sources of Radiation Exposure where 99% came from medical exposures

Cosmic Radiation, Terrestrial Radiation, Internal Radiation

Natural background radiation comes from the following major sources

Cosmic radiation

Radiation coming from the sun and stars. Differences in elevation, atmospheric conditions, and the Earth's magnetic field can change the dose of _____ that we receive.

Terrestrial radiation

The Earth itself and its atmosphere.

uranium, thorium and potassium

Main contributor of Terrestrial radiation

Exposure through inhalation

Largest contributor to natural radiation

radon and thoron

Sources of Exposure through inhalation

Exposure through ingestion

Ingestion of trace amount of radioactive minerals such as potassium-40 and carbon-14.

Atmospheric testing

From radioactive fall-out as a result of atomic weapons testing during the end of the 2nd world war

Nuclear power plants

releases regulated levels of radioactive material.

Industrial sources and commercial products

Nuclear gauges, smoke detectors, some glow-in-the dark exit signs, and radiation sterilization facility may expose humans.

Electromagnetic and Particulate Radiation

2 types of radiation

Particulate Radiation

a stream of atomic or subatomic particles that may be charged positively (alpha particles) or negatively (beta particles) or not at all (neutrons)

kinetic energy; mass in motion

Particulate radiation carry energy in the form of _____ or _____

“corpuscular” radiation

Other term for Particulate Radiation

Alpha particles

large subatomic fragments consisting of two protons and two neutrons identical to helium nucleus

+2

Charge of alpha particle

Beta Particles

High velocity electrons; Emitted by nucleus during radioactive decay

-1

Charge of Beta Particles

Positron or Beta positive particle

emitted from the nucleus of an atom during disintegration; anti-matter of electron, and it is therefore identical to the electron

+1

Charge of Positron or Beta positive particle

Neutron Radiation

energy released from an atom in the form of neutral particles called neutrons

Electromagnetic Radiation

Disturbance in space in the form of wave and carries no mass produced by a vibrating electric waves carrying both electric and magnetic fields

Photons

a stream of small "packets" of energy

3x10^8 (speed of light)

electromagnetic radiation travels in a straight line at what?

Electromagnetic Spectrum

the range of frequencies over which an electromagnetic radiation can be propagated.

Radio waves

have the longest wavelengths in the electromagnetic spectrum; carry signals for television and cellular phones

Radio waves

What is used in MRI

x-ray

produced by fast moving electrons that are suddenly decelerated

gamma rays

have the smallest wavelengths and therefore the highest energy among other types of electromagnetic radiation; These waves are generated by radioactive atoms during radioactive decays and in nuclear explosions

Wave Particle Duality

Electromagnetic radiation under certain conditions behaves as a wave and other times as a particle

waves

disturbances in a medium

transverse wave

EM waves travel in a form of

Velocity (c)

is the speed at which the wave travels

Wavelength (λ)

the distance between two successive crest

Frequency (ν)

the number of waves that passes a particular point per given time.

directly proportional

Energy of the EMR is _____ to frequency

inversely proportional

Energy of EMR is _____ to wavelength

Particle Theory

EMR acts as a small bundle of energy, known as photon or quantum. All photons carries a specific amount of energy that is dependent upon frequency. When photon interacts with matter, their interaction is similar to a particle.

Non-Ionizing radiation

Radiation that does not carry enough energy to dislodge an electron from an atom but can cause excitation of electron.

Ionizing radiation

radiation with enough energy to remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized.

Ionization

The removal of an orbital electron from an atom.

Directly ionizing radiation

includes all charged particles (electrons, positrons, protons, alpha particles, heavy ions) with sufficient energy to ionize atoms or molecules.

Indirectly ionizing radiation

includes x-rays, gamma rays, and all uncharged particles.