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