Radiation Physics Flashcards
Define…
matter
atom
energy
matter: anything that occupies space and has mass
atom: fundamental unit of matter
energy: occurs when matter is altered
a nucleus is composed of…
protons (positive)
neutrons (no charge)
electrons (negative)
Mass number/atomic weight Vs Atomic number
mass number: protons + neutrons
atomic number: number of protons equals number of electrons, is this number
List the letters for the electron orbits/shells
K (closest to nucleus and highest energy)
L
M
N
O
P
Q
What are the two ways molecules can be formed?
transfer of electrons
sharing electrons between outer shells
Ionizing radiation
energy is transmitted through space or matter (able to ionize)
ex// x-rays, gamma rays, alpha and beta particles
Nonionizing radiation
may excite stable atoms by raising an orbital electron to higher energy state
ex// visible light, infrared rays
Do we use x-radiation or radioactivity in dentistry?
x-radiation
Ion
an atom that gains or loses an electron and becomes electrically unbalanced
Negatively charged atom
gains an electron from an adjacent atom, more electrons than protons and neutrons
Positively charged atom
loses an electron and has more protons and neutrons
Ion pair
formed when an electron is removed from an atom
Particulate radiation
-tiny particles of matter that possess mass and travel in straight lines at high speeds
-transmit kinetic energy
Electromagnetic radiation
-propagation of wavelike energy (without mass) through space or matter
-man made or occur naturally
-magnetic fields at 90 degree angles and oscillating electrons
Beta particles
fast moving electrons emitted from nucleus of radioactive atoms
Alpha particles
emitted from the nuclei of heavy metals, exist as two protons and neutrons w/out electrons
Cathode rays
streams of high speed electrons that originate in the x-ray tube (electrons emitted)
Protons vs neutrons
protons: accelerated hydrogen nuclei
mass 1 charge +1
neutrons: accelerated particle
mass 1 no charge
List the properties of electromagnetic radiation
-no mass or weight
-no electrical charge
-travels at speed of light
-travels as both particle and a wave***
-propagate an electrical field at rights angles to path of travel
-propagate a magnetic field at right angles to the electrical field
-have different measuring energies
Particle concept of electromagnetic radiation
discrete bundles of energy called photons or quanta
-no mass
-no weight
-waves at speed of light
-travels in straight line
Which concept characterizes electromagnetic radiation
wave concept
Frequency
number of wavelengths that pass a given point in a certain amount of time
wavelength and frequency are _______ related.
inversely (if one is high other is low)
long wavelengths=
short wavelengths=
lazy
strong
use those first letters to remember😗
List the electromagnetic spectrum is order of lowest energy to highest
radio
microwave
infrared
visible light
ultraviolet
x-rays
gamma rays
Do x-rays have any mass or charge?
NO
Describe the speed and wavelength of x-rays
travels at speed of light
short wavelengths w/ high frequency
Describe the path of travel and focus capabilities of x-rays
travels path in straight line and can be deflected or scattered
cannot be focused to a point and will always diverge
Describe the penetrating power and absorption of x-rays
is able to penetrate liquids solids and gases, composition of the substance will effect whether it penetrates or is absorbed
x-rays are absorbed by matter; absorption depends on composition of the matter and the wavelength of the x-ray
Describe the ionizing capabilities of x-rays
high energy ionizing radiation
interacts with materials they penetrate and cause ionization
*can cause some structures to fluorescence
CATNAP
CAThode
Negative
Anode
Positive
List the components of the x-ray tubehead and their function
-metal housing (surrounds xray tube filled with oil)
-insulating oil (prevent overheating through absorption of heat)
-tubehead seal (aluminum or glass covering of tubehead, prevent exit of xray)
-xray tube (generates xray)
-transformer (alters voltage)
-aluminum disks (filters longer wavelengths)
Describe the x-ray tube
glass vacuum tube with all air removed from it
DC vs AC
DC: direct current- electrons flow in one direction
AC: alternating current- electrons flow in two opposite directions
Rectification
conversion of alternation currents (AC) to direct currents (DC)
Dental x-ray tubes act as ________.
self rectifiers; alternates AC into DC while producing x-rays
*ensures current is always flowing from cathode to anode
Amperage
measurement of the number of electrons moving through a conductor
Voltage
measurement of the electrical force that carries electrons from negative to positive poles
Low voltage circuits
-3 to 5 volts to heat filament
-regulates flow of electrical current to filament
-controlled by mA
High voltage circuits
-65k to 100k volts
-accelerates electrons from cathode to anode to produce the x-radiation
-controlled by kV
Transformer
-electromagnetic devices that allows a voltage of alternating current to be changed
-voltage may be increased or decreased
-supplies voltage to filament and anode
-step up, step down, or autotransformer
*routes current to x-ray tube**
Thermionic emission
occurs when the tungsten filament is heated by a current and electrons are released by the filament
List how x-rays are produced
- current enters control panel when unit turned on
- current goes from control panel to the tubehead through extension arm
- filament circuit uses 3-5 volts to heat tungsten filament
- heating of filament results in thermionic emission
- high voltage circuit activated when exposure button pushed
- electrons in the cloud accelerated across x-ray tube to anode
- cathode directs electrons to tungsten target
- electrons travel from cathode to anode
- when electrons strike tungsten target the kinetic energy is converted to x-rays and heat
- less than 1% is x-rays
- heat absorbed by insulating oil
- x-rays travel through unleaded glass window, tubehead seal, and aluminum filter
General (Braking) Radiation
attractive force between the bombarding electron and the nucleus of tungsten atom
consist of x-rays of many different energies and wavelengths
Characteristic Radiation
high speed electron dislodges an inner shell electron from the tungsten atom and causes ionization of that atom
account for a very small portion of x-rays produced
Define primary, secondary, and scatter radiation
primary: penetrating xray beam
secondary: x-rays produced when primary beam interacts with matter (less penetrating)
scatter: a form of secondary that is result of xray being deflected
No interaction
xray photon passes through the atom unchanged
*responsible for making densities on images and allow dental radiology to be possible:)
Photoelectric effect
xray photon collides with tightly bound inner shell electron, gives up all its energy to eject the electron from its orbit
*responsible for image contrast
Compton Scatter
*account for most of the scatter radiation
xray photon collides with loosely bound outer shell electron, photon loses some energy and continues in different direction at a lower energy
Coherent scatter
*aka unmodified scatter
low energy xray photon collides with an outer shell electron, photon has no change in energy only changes direction
*little effect on diagnostic imaging
