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Physics: Final Exam
| Question | Answer |
|---|---|
| Atomic number = ___________ | # of protons (**remember this is also the # of electrons bc there are the same number of protons and electrons) |
| Atomic mass = ___________________________ | # of protons and neutrons |
| What does the atomic number determine? | the chemical properties of the element and its place on the periodic table |
| Atomic mass is given in terms of ______. | amu |
| The same number of protons | isotopes |
| Different number of protons, but same number of neutrons. | isotones |
| Different number of protons and neutrons, but same atomic mass | isobars |
| Same atomic mass number and atomic number | isomers |
| Isomers are identical except for the fact that....? | they exist at different energy states due to differences in nucleon arrangement |
| Positively charged particles found in the nucleus of an atom. | protons |
| Neutral particles (no charge) also located in the nucleus. | neutrons |
| Negatively charged particles orbiting the nucleus. | electrons |
| Electrons fill each shell based on what? | principle quantum number (2n^2) |
| ____________ ___________ is the force between the nucleus and the orbiting electrons. | binding energy |
| This is defined as a pure substance made of only one type of atom, defined by its number of protons, and cannot be broken down into simpler substances by chemical means | element |
| This defined as a combination of two or more substances that are physically blended but not chemically bonded, and each retains its own properties | mixture |
| This is defined as a substance formed when two or more elements are chemically bonded together in fixed proportions. | compound |
| What is the numerical value of the speed of light? | 3x10^8 m/s |
| _____________ radiation is a combination of electrical and magnetic waves which travel at 90 degree angles. | electromagnetic |
| The only difference between x and y rays is what? | their origin |
| Electromagnetic radiation travels in a ______________ fashion. | sinusoidal |
| The distance from one crest to another | wavelength |
| Wavelength is represented by | lambda |
| The rate of rise and fall of a wave | frequency |
| Unit of measurement for frequency | Hz |
| Wavelength and frequency are _______________ proportional. | inversely |
| As wavelength becomes shorter, photon energy ____________. | increases |
| As frequency increases, photon energy _____________. | increases |
| Distance from the point of origin to a peak | amplitude |
| What determines energy/intensity of an EM wave? | amplitude |
| X and gamma rays are considered what type of radiation? | non-particulate |
| Particulate radiation is emitted from the _________. | nucleus |
| T or F. Particulate radiation can have a positive, negative, or neutral charge. | True |
| When does radioactive decay occur? | when the ratio of neutrons to protons in the nucleus is too high; an excess neutron transforms into a proton and an electron; the proton stays in the nucleus and the electrons is ejected energetically |
| What is the decay constant? | lambda |
| This is the time required for either the activity or the # of radioactive atoms to decay to half the original or initial value. | half-life |
| What happens to the atomic number and atomic mass in alpha decay? | the atomic mass decreases by 4 and the atomic number decreases by 2 |
| Beta decay results in an ejection of what? | a negatron or positron |
| For radionuclides with a high neutron to proton ratio and an antineutrino, this tends to eject a _____________. | negatron |
| For radionuclides with a low neutron to proton ratio and a neutrino, this tends to eject a _____________. | positron |
| Eventually the positron combines with an electron and produces what? | annihilation radiation |
| Which type of radioactive decay has an orbital electron captured by a nucleus and changes a proton into a neutron? | electron capture |
| T or F. Electron capture radioactive decay competes with positron decay to increase neutron to proton ratio. | True |
| What happens after the electron is captured in electron capture radioactive decay? | a gamma ray is emitted |
| Since electron capture radioactive decay mostly causes k-shell electron to leave its original atom what does this cause? | characteristic x-rays and auger electrons |
| This radioactive decay process happens when excess nuclear energy is transferred to an orbital electron which is then ejected. | internal conversion (IC) |
| What is the kinetic energy formula for internal conversion? | KEe-= NRG (released by nucleus) - NRG (binding) |
| This radioactive decay process is when an excited state persists for a measurable amount of time and is "metastable" | Isomeric transition (IT) radioactive decay |
| A "metastable" nucleus is an isomer of the final product meaning same atomic number and mass but different ___________. | energy |
| Penumbra Formula | Pd= S(SSD-SDD)/SDD |
| What is a classic property of electromagnetic radiation that represents a decrease in intensity at the edge of the field? | penumbra |
| This is the variation in X-ray intensity across the beam, with higher intensity on the cathode side and lower intensity on the anode side, due to the absorption of X-rays within the anode. | heel-effect |
| This is the maximum variation of the beam's intensity. | flatness |
| This is the measure of the beam equality from side to side. | symmetry |
| This is the point in space around which the machine rotates. | isocenter |
| The higher the beam energy the more _______________ ability it has. | penetrating |
| The lower the energy the ___________ the skin sparing effect. | lower |
| Which type of interaction is the most common for xray production? | Brems |
| How are characteristic xrays produced? | an electron hits an orbital electron which causes it to be knocked out of orbit and this causes outer shell electrons to fill in the space which releases energy in the form of a photon |
| What are the cardinal principles of radiation protection? | time, distance, shielding |
| This type of filter is used in orthovoltage therapy and it selectively filters out low energy xrays and subsequent emissions from the material behind. | thoraeus |
| What are the components of a thoraeus filter? | TIN-Cu-Al |
| The measurement of ionization produced in air by photons. | exposure |
| Why is it important to ensure the dose profiles are flat? | bc you want to make sure the entire treatment field is getting radiation delivered evenly/symmetrically |
| This technique is where the isocenter is placed within the patient, and the patient does not move between treatment fields. | isocentric (SAD) technique |
| This technique is where the isocenter is placed on the patient's skin, and the patient moves between treatment fields. | SSD technique |
| transports the microwave power from the magnetron/klystron to the accelerator guide | waveguide |
| vacuum tube made of copper that is divided by diaphragms in varying diameter and space | accelerator guide |
| what type of accelerator guide is shorter and more common, changes its amplitude with time rather than position, uses a forward and backward traveling wave and the circulator prevents excess energy from being reflected back into other components | standing |
| senses the optimum operating frequency of the accelerator in order to maximize the radiation output | automatic frequency control |
| ___________ is manmade. Produced in a nuclear reactor and is more effective than x-ray but less than a LinAc | cobalt-60 |
| graphic representation of the radiation dose across a given treatment field | dose profile |
| Dose Profiles are constructed by taking measurements across the field at _________ using a dosimeter | central axis |
| At low energies, the _______ effect is the most prominent radiation effect | photoelectric |
| In the therapeutic range, the _____ effect and ____ ______are the most prominent | compton and pair production |
| the highest dose that can be deposited | Dmax |
| The high voltage power supply provides ___ ___ power to the modulator in pulses of microsecond durations | direct current |
| Direct Current pulses are delivered to the ______/_______ AND the ______ gun simultaneously | magnetron/klystron; electron |
| what produces the microwave radiation used by the wave guide to accelerate electrons to the desired kinetic energy | radiofrequency power generation system |
| What two components make up the Radiofrequency Power Generation Sytem | RF power source and a pulsed modulator |
| what are the 2 examples of a radiofrequency power source | magnetron and klystron |
| cabinet usually located in the treatment room or nearby that contains a pulse framing network | modulator |
| PRODUCES microwaves, found in lower energy machines, less costly but less stable, average lifetime is 1 year but can be extended by running at lose dose rates | magnetron |
| Microwave AMPLIFIER, found in higher energy machines | klystron |
| prevents the microwave power from being deflected back into the magnetron or klystron | circulator |
| acts as a traffic cop by allowing only selected energies to reach the accelerator guide | circulator |
| source of electron that shoots the electrons into the accelerator guide, energy is about 40-50KV | electron gun |
| What are the two types of electron guns | diode and triode |
| contains a heated filament cathode which boils off a cloud of electrons and a grounded anode | diode |
| contains a heated filament cathode which boils off a cloud of electrons and a grounded anode, incorporates a grid between the cathode and anode to collect a portion of the liberated electrons | triode |
| what are the two types of accelerator guide | standing and traveling |
| what type of accelerator guide is similar to a wave on a beach, electrons are accelerated through the waveguide in a manner similar to a surfer | traveling |
| Electrons exit the accelerator guide and enter the | bending magnet |
| eliminates lower energy electrons, focuses the electrons into a pencil thin 3mm beam | bending magnet |
| 3 systems of the bending magnet | 90, 270, and 112.5 degrees |
| The transmission target is mounted on a carousel for ____ energies | dual |
| what cannot be adjusted and limits the maximum field sized for treatment to 40 x 40cm | primary (fixed) collimators |
| mounted on carousels for easy movement, made of various metals, and use is determined by machine mode: photon vs electron | flattening filter/scattering foil |
| used for photon beams, cone-shaped filters that are energy specific, and attenuates the dome of the photon beam in order to provide a more flat and symmetrical dose distribution | flattening filter |
| used for electron beams, spreads out the pencil-thin 3mm electron beam that exits the bending machine | scattering foil |
| permanently sealed, transmission ionization chambers that measure the dose rate, integrated dose, and field symmetry. Positioned between the flattening filter/scattering foil and secondary collimator | dose monitoring system |
| Why is it important to have dual ionization chambers in a LINAC? | this provides accuracy for dose monitoring and provides reliability since the second acts as a backup if there is any malfunction of the first. |
| adjusted for field size, composed of concrete, lead, and/or tungsten, maximum field size of 40cm x 40cm | secondary (variable) collimators |
| Provides the extremely low pressures needed for the operation of the electron gun, acceleratory guide, and the bending magnet | vacuum |
| what auxiliary equipment of a LinAc is constructed of steel and concrete and absorbs 99.9% of the primary beam | beam stopper |
| Why are Electron Cones placed so close to the patients skin | bc they have to be focused |
| This is done to minimize exposure to workers and general public | room shielding |
| Room Shielding Protection is required against | primary, scatter, and leakage radiation |
| any surface that you can aim the radiation beam towards the floor, ceiling, and adjacent walls | primary barrier |
| must attenuate scatter radiation. opposing walls at the head and foot of the table and the vault door | secondary barrier |
| radiation working spaces, access is controlled, radiation exposure is assumed to be .1 rem/wk | controlled area |
| public areas, radiation exposure assumed to be .01 rem/wk | uncontrolled area |
| T or F. Treatment rooms must have video monitors and audio intercoms | true |
| What are the 3 emergency LinAc considerations | beam off, emergency off, and code button |
| What is the treatment dose from a Cobalt-60 machine based on | time |
| What is the half-life of Cobalt-60 | 5.26 years |
| How much must treatments be corrected each month | 1.09% |
| What is the average gamma emissions for Cobalt-60 | 1.25 MeV |
| In case of a power failure with Cobalt-60 what should you do | call physics, comfort the patient, no emergency procedure |
| What should you do if the source of a cobalt-60 machine fails to retract? | remove patient from the room, seal the room, and call physics |
| Explain how photoelectric effect occurs. | A photon interacts with and ejects and bound electron, and all energy is transferred to this electron which creates a photoelectron. |
| After the ejection of the electron in the PE, what happens? | a vacancy is open in that shell and the atom is in an excited state which causes the cascade effect |
| The probability of PE to occur depends on photon ________. | energy |
| What does the PE depend strongly on? | atomic number of material |
| PE is proportional to _______. | Z^3 |
| PE is __________ proportional to E^3 and ____________ proportional to Z^3 | inversely;directly therefore, PE is proportional to Z^3/E^3 |
| The greatest effect of PE is with ________ atomic number and _________ energy. | high;low |
| With the compton effect, a photon interacts with a _________ electron. | free |
| How does the compton effect occur? | the electron gets some of the photon energy and is emitted at a small angle, and the photon is scattered at a small angle with less energy than it originally had. |
| With compton effect, the photon energy is ______ than the binding energy of the electron. | greater than |
| Compton effect decreases with _____________ photon energy. | increasing |
| Compton effect depends on electron ___________. | density |
| In pair production, the photon energy is greater than _______ MeV. | 1.02 (this is bc resting energy is .511 and then multiply that by 2 bc it is a pair = 1.02) |
| Explain how pair productions occurs. | A photon interacts and gets an e- and e+ pair which tends to be ejected in forward direction relative to the photon. |
Created by:
lheard
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