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152 Cards in this Set

  • Front
  • Back
what is matter?
anything that occupies space & has mass
when does energy result?
when matter is altered.
what is the fundamental unit of matter?
an atom
the atom consists of 2 parts, what are they?
central nucleus and orbiting electrons
how is the identity of an atom determined?
by its composition of its nucleus and the arrangement of its orbiting electrons
at present, how many different atoms exist?
105
the dense core of the atom composed of particles is known as what?
nucleus
nucleus is composed of what?
protons and neutrons(also known as nucleons)
the nucleus of an atom occupies very little space, most of the atom is empty space. t/f
true
what determines the mass number or atomic weight?
the number of protons and neutrons in the nucleus of an atom.
atomic number is determined by what?
number of protons inside the nucleus equals the number of electrons outside the nucleus
elements are substances made up of only one type of atom. t/f
t
electrons travel around the nucleus in well defined paths known as what?
orbits or shells
what is the max number of shells that an atom contains?
seven
each shell is at at different distances from the nucleus and this represents different energy levels. what letters designate the shell?
K-Q.
which energy shell is located closest to the nucleus?
Kshell
which shell has the highest energy level?
k shell
electrons are maintained in their orbits by what force?
electrostatic force
the binding energy or binding force of an electron is what?
the attraction btwn the positive nucleus and negative electrons
what determines the binding energy?
the distance btwn the nucleus and the orbiting electron and it's diff for each shell
the strongest binding energy is found closest to the nucleus in what shell?
k shell
electrons located in the outer shells have a stronger or weaker binding energy?
weak
the binding energies of orbital electrons are measured in what measurements?
electron volts (eV) or kil electon volts (keV)
one kil elecron volt equals how many eVs?
1000
the energy required to remove an electron from its orbital shell must exceed what?
the binding energy of the electron in that shell
atoms are capable of combing with each other to form what?
molecules
how is a molecule defined?
as two or more atoms joined by chemical bonds
OR
the smallest amount of a substance that possesses its characterstic properties
molecules are formed in one of two ways. what are the two ways?
1. by the transfer of electrons
2. by the sharing of electrons btwn the outermost shells of atoms
a neutral atom contains equal numbers of protons and electrons. t/f
t
an atom that gains or loses an electron and becomes electrically unbalanced is known as what?
an ion
ionization is what?
the production of ions or the process of converting an atom into ions
ionization deals only with electrons and protons & requires sufficient energy to overcome the electrostatic force that binds the electron to the nucleus. t/f
f: it only deals with electrons
when an electron is removed from an atom in the ionization process, what results?
an ion pair
when an ion pair is formed, which is the positive ion and which is the negative one?
the atom is positive ion and the electron that is ejected is the negative ion
radiation is what?
the emmision and propagation of energy through space or a substance in the form of waves or particles.
radiation and radioactivity basically have the same meaning. t/f
f. they DO NO have the same meaning.
Radioactivity is defined as what?
the process by which certain unstable atoms or elements undergo SPONTANEOUS disintegration or decay, in an effort to attain a more balanced nuclear state.
if a substance gives off energy in the form of particles or rays as a result of the disintegration of atomic nuclei, it is considered what?
radioactive
in dentistry, what is used? radiation or radioactivity?
radiation, specifically x-radiation
ionizing radiation is defined as what?
radiation that is capable of producing ions by removing or adding an electron to an atom
ionizing radiation is classified into 2 groups: _______ and _______
particulate radiation
and
electromagnetic radiation
radiation that is capable of producing ions by removing or adding an electron to an atom is known as what?
ionizing radiation
what's particulate radiations?
tiny particles of matter that possess mass and travel in straight lines and at high speeds
what type of radiation transmits kinetic energy by means of their extremely fast moving, small masses?
particulate radiations
four types of particulate radiation are recognized. what are they?
1. electrons (beta particles = fast moving electrons from the nucleus of radioactive atoms. cathode rays = streams of high speed electrons originating from xray tube)
2. alpha particles
3. protons
4. neutrons
electrons can be classified into 2 categories. what are they & their origins?
1. beta particles = fast moving electrons emited from NUCLEUS of radioactive atoms
2. cathode rays = streams of high speed electrons that originate in an xray tube
alpha particles are emitted from where? and how do they exist?
alpha particles are emitted from the nuclei of heavy metals and exist as TWO protons and neutrons, without electrons
alpha particles: do they have electrons, protons or neutrons? or all 3?
only protons and neutrons. NO electrons
protons are accelerated particles, specifically what type of nuclei? what mass and what charge?
hydrogen nuclei.
mass of 1.
charge of +1.
neutrons are accelerated particles with mass of what and charge of what?
mass of 1.
no charge.
define electromagnetic radiation
propagation of wavelike energy (without mass) through space or matter.
why the term electromagnetic?
bc energy propagated is accompained by oscillating electric & magnetic fields positioned at right angles to one another
oscillating electric and magnetic fields are characterstics of what type of radiations?
electromagnetic
which type of radiations have:
no mass
no weight
no electrical charge
travel at the speed of light (3x10^8m/s)
travel both as a particle and a wave
?
electromagnetic radiations
which radiation:
-propagates as an electric field at RIGHT angles to path of travel
-propagate a magntetic field at right angles to the electric field
-has different measurable energies (frequencies and wavelengths)
electromagnetic radiations
what are examples of electromagnetic radiations?
cosmic rays, gamma rays, xrays, UV rays, visible light, IR, radar waves, microwaves and radio waves
electromagnetic radiations are arranged according to their energies into what?
the electromagnetic spectrum
electromagnetic radiations can be classified as:
ionizing
or non-ionizing
only high energy radiations are capable of ionization in the electromagnetic spectrum. t/f
t
what are examples of high energy radiations
cosmic rays
gamma rays
xrays
what are the 2 concepts when dealing wtih electromagnetic radiations?
particle concept
and
wave concept
bc it can travel through space as both a particle and a wave
the particle concept characterizes electromagnetic radiations as descrete bundles of energy called?
quanta or photons
do photons or quanta contain weight or mass? how much
no. none!
wavelength is the distance btwn what?
the crest/peak of one wave and the crest of the next
the wave concept characterizes electromagnetic radiations deals with what 3 concepts?
velocity
wavelength
frequency
velocity = speed of the wave. how fast do electromagenetic radiations travel?
speed of light
3 x 10^8 m/s or 186,000 miles per second
wavelength determines the energy and what?
penetrating power of hte radiation
the shorter the distance btwn crests, the shorter the wavelength and the ______ the energy and ability to penetrate matter
HIGHER
what unit is wavelength measured in?
nanometers for short waves, and meters for longer waves
frequency is the number of _______ that pass a given point in a certain amount of _____.
wavelengths
time
the shorter the wavelength, the higher the frequency. t/f
t
low frequency = longer waves = _____ energy.
less.
the 3 components parts of dental xray machine are what?
1. control panel
2. extension arm
3. tube head
dental xray machine can be divided into 3 study areas =
1. component parts
2. xray tube
3. xray generating apparatus
what am i? i am the metal body of hte tubehead that surrounds the xray tube and transforms and is filled with oil. i protect the xray tube and ground the high voltage components
metal housing
what am i? i'm the oil that surrounds the xray tube and transforms insdet he tubehead, i prevent overheating by absorbing the heat created by the production of xrays
insulating oil
what am i? i am the aluminum or leaded glass covering of the tubehead that permits the exit of xrays from the tubehead. i seal the oil int he tubehead and act as a filter to the xray beam.
tubehead seal
what am i? i am the heart of hte xray generating system
x ray tube
what am i? i'm a device that alters the voltage of incoming electricity
transformer
what am i? sheets of 0.5 mm thick aluminum placed in the path of hte xray beam, i filter out hte non penetrating, longer wavelength xrays.
aluminum disks
what am i? i am the lead plate with a central hole that fits directly over the opening of the metal housing where the xrays exit, i restrict the size of the xray beam
lead collimator
what is the collimator made out of?
lead
what am i? i am the open ended lead lined cylinder that extends from the opening of the metal housing of the tubehead and i aim and shape the xray beam
PID = position indicating device
what does the leaded glass housing do?
prevents xrays from escaping in all directions
the cathode consists of what 2 things?
tungsten filament producing electrons when heated
and
molybdenum cup which focuses the electrons into a narrow beam, directing the beam across the tube toward the tungsten target of hte anode
what's the purpose of hte anode?
to convert electrons into xray photons
what is the anode composed of?
tungsten target (serves as a focal spot, convering bombarding electrons into xrays)
and
copper stem (dissipates the heat away from the tungsten target)
copper stem does what?
dissipates the heat away from the tungsten target
tungsten target does what?
serves as a focal spot, convering bombarding electrons into xrays
tungsten filament does what?
produces electrons when heated
what does the molybdenum cup do?
focuses electrons into a narrow beam, directing it across the tube towards the anode target
electricity is defined as?
the energy used to make xrays
the flow of electrons is known as the?
electric current
direct current occurs when electrons flow in ___ direction through the conductor.
one
alternating current (AC) describes what?
electrical current where electrons flow in two opposite directions
rectification is what?
conversion of AC into DC
conversion of AC into DC is known as what?
rectification
the dental xray is a self-rectifier and changes ____ into _____ while producing xrays, ensuring current is flowing from cathode to anode.
AC into DC
constant-potential machines reduce patietn exposure to radiation by ___%
20%
what is the measurement of hte number of electrons moving through a conductor?
amperage
current is measured in what?
A = amperes
or
mA = miliaperes
voltages is measured in?
volts or kilvolts
voltage is?
the measurement of electrical force that causes electrons to move from a negative pole to a positive one
amperage = number of electrons passing through the ___ filament and can be increased or decreased by what adjustment?
cathode filament
miliamperage adjustment
the voltage of the xray tube current, or the current passing from the cathode to the anode is controlled by what?
kilovoltage peak kVp
kilovoltage peak controls what?
the voltage of the xray tube current, or the current passing from the cathode to the anode
circuits are paths of electrical current. the low voltage circuit is also known as?
filament circuit
filament circuit (low voltage) uses how many volts?
65,000 to 100,000 volts.
transformers are devices that do what?
increase or decrease the voltage in an electrical circuit
in the production of dental xrays, 3 transformers are used to adjust the electrical circuits. what are they?
1. step down transformer
2. step up transformer
3. autotransformer
the step-down transfoerm decreases the voltage from the INCOMING 110 or 220 line voltage to what?
3 - 5 volts used by the filament circuit
what side has the more coils in a step down transformer?
the primary coil(the voil receiving the alternating electrical current, or input coil)
the secondary coil is the output coil, while the primary coil is the input coil. t/f
t
the step up transformer increases the voltage from the incoming 110 or 220 line voltage to what?
65,000 to 100,000 volts used by the high voltage circuit.
the step up transformer has more coils on which coil?
secondary coil
general radiation is known as different names such as?
braking radiation
or
bremsstrahlung radiation
why is it called braking radiation?
sudden stopping of high speed electrons when they hit the tungsten target int he anode
70% of hte xray energy produced at the anode can be classified as which type of radiation?
general radiation
when an electron that passes close to the nucleus of a tungsten atom is slowed down, an xray photon of lower energy known as __________ results.
general (braking) radiation
general radiation consists of xrays of few, moderate, or many different energies and wavelengths?
MANY
characteristic radiation is produced when?
when a high speed electron dislodges an inner shell electron from the tungsten atom and causes ionization of that atom. rearrangement occurs and prodces a loss of energy resulting in xray photon production
characterstic radiation accounts for a very small part of xrays in the dental field. t/f
t
characteristic radiation occurs only at ________ kVp bc why?
70 kVp and above.
bc the binding energy of hte K shell electron is approx 70 keV
primary radiation refers to what?
the penetrating xray beam produced at the target of the anode and that exits the tube head
primary radiation is often referred to what 2 other terms?
primary beam
or
useful beam
secondary radiation is what?
refers to xradiation that is created when primary beam interacts with matter (skull)
a form of secondary radiation that results when an xray is deflected is called what?
scatter radiation
when xray exits tubehead 3 things can happen. what are they?
1. xrays can pass through the patient without any interaction
2. xray photons can be completely absorbed by the patient
3. xray photons can be scattered
four possibilities can occur (at the atomic level) when an xray photon interacts with matter. what are they?
1. no interaction
2. absorption or photoelectric effect
3. compton scatter
4. coherent scatter
is it possible for an xray photon to pass through matter or the tissue of a patient without any interaction?
yes
the xray photons that pass through a patient without interaction are responsible for producing ______ on the film
densities
absorption =
total transfer of energy from xray photon to the atoms of matter through which the xray beam passes.
at the atomic level, absorption occurs as a result of the ______ effect.
photoelectric effect
in the photoelectric effect, ionization occurs. t/f
t
the ejected electron (during hte photoelectric effect) is termed what? and what charge is it?
photoelectron and has a negative charge
when an xray photon collides with an inner shell electrion, a ________ effect occurs: the photon is absorbed and ceases to exist and a ________ with a negative charge is produced
photoeletric effect
photoelectron
compton scatter occurs when an xray photon is deflected from its path during its passage through matter. t/f
t
most of the scatter radiation is due to what effect?
the compton effect
ionization takes place in compton scatter as well as the photoelectric effect.t/f
t
when an xray photon collides with a loosely bound outer shell electron and gives up part of its energy to eject the electron from its orbit, what type of scatter occurs?
compton
in compton a newer xray photon is produces. does it have lower or higher energy?
it's weaker with lower energy
the ejected electron in compton scatter is refered to as what? and what charge does it have?
comtpon electron
or
recoil electron.
negative charge
compton scatter accounts for ______ % of the scatter that occurs in diagnostic radiography.
62%
coherent scatter occurs when?
xrays interact with matter
another name of coherent scatter is what?
unmodified scatter
when an xray photon is scattered and NO loss of energy occurs, what scatter is this?
coherent scatter
when a low energy xray photon interacts with an outer shell electron this is known as what type of scatter? no chnage in the atom occurs
coherent
no loss of energy, no ionization occur in what scatter?
coherent
which types of scatter have ionization? which don't?
ionization: compton, photoelectric
no ionization: coherent
it's called "unmodified" scatter why?
bc it simply undergoes a CHANGE IN DIRECTION without a change in energy!
coherent scatter accounts for ___% of interactions of matter with the dental xray beam.
8%
list the % for photoelectric, compton, and coherent scatters
photoelectric: 30%
compton scatter: 62%
coherent scatter: 8%