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Radiologic Physics > Physics 13-1 Final > Flashcards

Physics 13-1 Final Flashcards

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0
Q

What is located btw step-up transformer and XR tube?

A

rectifier

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1
Q

What is located btw the auto-transformer and step-up transformer?

A

kVp meter

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2
Q

what is located at secondary side of step-up transformer?

A

mA meter

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3
Q

two basic types of induction?

A

self and mutual

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4
Q

a transformer converts:

A

electrical potential to higher or lower intensity

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5
Q

What works under the principle of self-induction?

A

auto-transformer

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6
Q

what determines quality of XR?

A

kVp

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7
Q

what determines quantity of XR?

A

mA and exposure time

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8
Q

heating of a coil of wire to produce electrons

A

thermionic emission

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9
Q

flow of electrons from filament to anode

A

tube current

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10
Q

what converts A/C to D/C?

A

rectifier

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11
Q

the current to a transformer must be supplied by a(n)

A

A/C source

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12
Q

variations in power distribution to XR are corrected by the

A

line voltage compensator

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13
Q

the first component to receive power in the XR circuit is

A

the auto-transformer

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14
Q

what circuit provides electrons for the XR tube current?

A

filament

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15
Q

thermionic emission at the filament determines the __________ across the XR tube during an exposure

A

milliamperage

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16
Q

step-down transformer is located in the ________ circuit

A

filament

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17
Q

most accurate type of timer

A

electronic

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18
Q

the AEC terminates the exposure when

A

sufficient rad reaches the IR

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19
Q

location of ionization chamber

A

btw pt and IR

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20
Q

f(x) of photodiode

A

convert light to electric signal

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21
Q

the principle material used in the formulation of a solid state diode

A

silicon

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22
Q

process by which A/C is converted to pulsating D/C

A

rectification

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23
Q

type of unit most likely to possess the smallest voltage ripple

A

high frequency unit

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24
Q

a 3 phase 12 pulse wave form has ___ ripple

A

4%

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25
Q

a high frequency wave form has ___ ripple

A

1%

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26
Q

a 3 phase 6 pulse unit has an effective kV of about ____ of the peak kVp

A

86%

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27
Q

during capacitor discharge, the voltage falls at a rate of

A

1 kV/mAs

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28
Q

the electron cloud around the filament

A

space charge

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29
Q

tungsten is the material of choice for the target b/c of what 3 reasons?

A

high atomic #, high thermal conductivity, high melting point

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30
Q

“the effective focal spot size is always SMALLER than the actual focal spot size”

A

line focus principle

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31
Q

smaller the anode angle, the _______ the heel effect

A

larger

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32
Q

anode angle and effective focal spot size are

A

directly proportional

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33
Q

anode angle and heel effect are

A

indirectly proportional

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34
Q

taking advtg of heel effect, thicker anatomical parts positioned under the

A

cathode

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35
Q

the effective focal spot size is larger on what side?

A

cathode

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36
Q

most frequent cause of tube failure

A

electron arcing from the filament

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37
Q

what controls the duration of the XR exposure?

A

timing circuit/exposure switch

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38
Q

what can be adjusted to control the quantity of the XR

A

mA selector

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39
Q

what is capable of manipulating the input voltage into the XR circuit

A

line compensator

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40
Q

what controls the voltage in the filament circuit

A

step-down transformer

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41
Q

what can be adjusted to increase the penetration power of the XR

A

kVp selector

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42
Q

the smallest quantity of electromagnetic energy

A

photon

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43
Q

in sine wave, D from crest to crest (valley to valley)

A

wavelength

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44
Q

of wavelengths that pass a point of observation per second

A

frequency

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45
Q

in sine wave, the shorter the wavelength, the _____ its frequency

A

higher

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46
Q

energy of a photon is directly proportional to its

A

frequency

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47
Q

only diff btw XRs and gamma rays

A

origin

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48
Q

describes the relationship btw rad intensity and the D from the rad source

A

inverse square law

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49
Q

when white light goes through a prism

A

refraction

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50
Q

study of fixed/stationary electric charge

A

electrostatics

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51
Q

fundamental unit of electric charge

A

coulomb

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52
Q

“electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the D btw them”

A

Coulomb’s law

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53
Q

“when an object becomes electrified, the electric charges are uniformly distributed throughout the object or on its surface”

A

electrostatic law #3

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54
Q

“electric charge of a conductor is concentrated along the sharpest curvature of its surface”

A

Electrostatic Law #4

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55
Q

unit of electric potential

A

volt

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56
Q

silicone and germanium

A

semiconductors

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57
Q

the property of some materials to exhibit no resistance below certain critical temps

A

superconductivity

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58
Q

any property of the circuit that opposes/hinders the flow of the current

A

resistance

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59
Q

4 factors that affect resistance (of conductor)

A

material, diameter, length, temp

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60
Q

“voltage across the total circuit (or any portion thereof) is equal to the current multiplied by the resistance”

A

Ohm’s law

61
Q

electrons flowing alternatively in opposite direction

A

A/C

62
Q

____ is equal to one ampere of current flowing through an electric potential of 1 volt

A

1 watt

63
Q

any charged particle in motion creates…

A

magnetic field

64
Q

the direction of the magnetic field is _______ to the motion of a charged particle

A

perpendicular

65
Q

ability of a material to attract the lines of magnetic field intensity

A

magnetic permeability

66
Q

degree to which various materials can be magnetized

A

magnetic susceptibility

67
Q

what is considered paramagnetic?

A

MRI contrast

68
Q

what works under the principle of self-induction?

A

auto-transformer

69
Q

what represents transformer law?

A

Vs/Vp=Ns/Np

70
Q

transformer loss due to the resistance of the wire

A

copper loss

71
Q

an electric current can be induced in a coil of wire if its placed near a(n)

A

electromagnet

72
Q

reduction of rad intensity due scattering/absorption

A

attenuation

73
Q

gamma rays are produced in the ______ of an atom

A

nucleus

74
Q

photons w the highest frequencies have the

A

shortest wavelengths

75
Q

electrostatic force is _______ proportional to the D btw charges and _______ proportional to the product of the charges

A

inversely, directly

76
Q

the charges on an electrified object are distributed

A

evenly throughout the object

77
Q

_____ is a source of D/C

A

battery

78
Q

an A/C is represented by a _______ line

A

sinusoidal

79
Q

What is Ohm’s law?

A

V=IR

80
Q

SI unit of magnetic field strength

A

tesla

81
Q

what type of material can be made magnetic when placed in an external magnetic field?

A

ferromagnetic

82
Q

quantity of matter as described by its energy equivalence

A

mass

83
Q

has form, occupies space

A

matter

84
Q

ability to do work

A

energy

85
Q

rate of doing work

A

power

86
Q

measures occupational dose

A

rem

87
Q

measures rad in air

A

roentgen

88
Q

SI unit of mass

A

kg

89
Q

atoms and molecules are the fundamental building blocks of ______

A

matter

90
Q

radio waves, light, XRs

A

electromagnetic energy

91
Q

ionizing rad is capable of removing _______ from atoms as it passes through matter

A

electrons

92
Q

largest source of manmade ionizing rad in public

A

diagnostic XRs

93
Q

Wilhelm Roentgen discovered XRs while experimenting w the

A

Crookes tube

94
Q

radioactive material measured in

A

curies

95
Q

Ex of ionizing rad

A

gamma rays

96
Q

velocity of light

A

3 x 10^8 m/s

97
Q

Newton’s 2nd law

A

F=MA

98
Q

a measure of 10^-3 rads is a

A

millirad

99
Q

who invented fluoroscopy?

A

Thomas Edison

100
Q

“atom” 1st used by

A

the greeks

101
Q

smallest particle that has all the properties of an element

A

atom

102
Q

who developed the periodic table?

A

mendeleev

103
Q

pos charged nucleus surrounded by neg charged electrons in well-defined orbits

A

Bohr atomic model

104
Q

fundamental particles of an atom

A

neutron, proton, electron

105
Q

the chem element is determined by the # of?

A

protons in the atom

106
Q

binding energies/energy levels of electrons are represented by their

A

shells

107
Q

atom w same # of protons, but diff # of neutrons

A

isotope

108
Q

when atoms of various elements combine, they form

A

molecules

109
Q

atom that gains/loses 1+ electrons

A

ion

110
Q

max # of electrons that can exist in an electron shell is calculated by

A

2n^2

111
Q

innermost electron shell

A

K

112
Q

shell # aka

A

principal quantum #

113
Q

the least penetrating form of ionizing rad

A

alpha particles

114
Q

the _____ of electromagnetic rad is constant

A

velocity

115
Q

T required for a quantity of radioactivity to be reduced to 1/2 its original value

A

half life

116
Q

alpha particles are compared to a _______ nucleus

A

Helium

117
Q

the force that keeps an electron in orbit is the

A

centripetal and centrifugal forces

118
Q

How do you convert Fahrenheit to Celsius?

A

Tc = 5/9 (Tf - 32)

119
Q

How to calculate HU for 3 phase, 6 pulse?

A

HU=kVp x mA x s x 1.35

120
Q

How to calculate HU for 3 phase, 12 pulse?

A

HU=kVp x mA x s x 1.41

121
Q

equation for kinetic energy

A

KE=1/2mv^2

122
Q

How do you increase the KE of electrons traveling from filament to anode?

A

raise kVp

123
Q

what happens to KE of projectile electron when it interacts w tungsten target?

A

converts to 99% thermal energy and 1% electromagnetic XR

124
Q

Characteristic rad?

A

XR released as result of photoelectric effect (when projectile electron interacts w K-shell of target)

125
Q

relationship of effective energy of the char rad and the atomic number of the target material

A

direct

126
Q

type of rad when projectile electron interacts w nuclear field of target atom

A

Bremsstrahlung

127
Q

in diagnostic range, most XRs are

A

Brems

128
Q

min kVp required to produce char rad

A

69 kVp

129
Q

at 100 kVp, what percentage is char and brems?

A

15% char, 85% Brems

130
Q

char rad has what type of energy

A

fixed/discrete

131
Q

15% rule?

A

15% increase in kVp is equal to doubling mAs (to keep a constant optical density)

132
Q

What 4 factors affect XR quantity?

A

current/mAs, volt/kVp, filtration, D

133
Q

What 2 factors affect XR quality?

A

volt/kVp, filtration

134
Q

mAs/current does what to quant and qual?

A

+ quant, n/a qual

135
Q

kVp/voltage does what to quant and qual?

A

+ quant, + qual

136
Q

filtration does what to quant and qual?

A
  • quant, + qual
137
Q

Z does what to quant and qual?

A

+ quant, + qual

138
Q

voltage ripple does what to quant and qual?

A
  • quant, - qual
139
Q

D does what to quant and qual?

A
  • quant, - qual
140
Q

formula btw XR quant and mAs?

A

I1/I2=mAs1/mAs2

141
Q

formula btw XR quantity and kVp?

A

I1/I2=(kVp1/kVp2)^2

142
Q

Is XR quant proportional to kVp?

A

yes, change in quant proportional to the square of the ratio of kVp (if kVp doubled, I increases by factor of 4)

143
Q

formula btw XR quant and D?

A

I1/I2=(D2/D1)^2

144
Q

formula and aka for direct square law?

A

density maintenance law; mAs1/mAs2=D1^2/D2^2

145
Q

what is meant by quality?

A

energy/penetrating ability

146
Q

what is HVL?

A

thickness of absorbing material necessary to reduce XR I to 1/2 its original value

147
Q

best method to specify XR quality?

A

HVL

148
Q

total filtration?

A

inherent (0.5mm Al) + added (1mm Al) + mirror (1mm Al) = 2.5mm Al

149
Q

purpose of compensating filter?

A

produce uniform density of a nonuniform object aka “wedge filter”

Radiologic Physics (2 decks)

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