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Physics exam 2

QuestionAnswer
Isotropic Equal intensity in all directions
Leakage radiation Secondary radiation emitted through the tube housing
What makes a diode 2 electrodes (anode and cathode)
Purpose of tube housing For mechanical support and shock prevention
Purpose of oil surrounding tube Provides electrical insulation; dissipates heat which oil absorbs and allows heat to carry it from the tube
Problems with filament vaporization It costs glass enclosure which causes arcing and tube failure
Quality= Energy
Which side of x ray tube is negative Cathode
Thermionic emission Filament is electrically heated causing electrons to boil off the surface of the filament
Focusing cup Electrostatically confines the electron beam to a small area of the anode
2 ways the allow focusing cup to focus electron beam Shape of cup and small negative charge
Dual focus tube 2 focal spots
Compare small focal spot to large focal spot Smaller focal spot will give sharper images and large produces blurry images
Positive side of x ray tube Anode
Production of heat to X-ray in tube 99% heat 1% x ray
Why is tungsten used for target in X-ray tube High melting point 3370 C and high atomic number Z=74 and it's cheap
Benefits of rotating anode Greater heat capacity
Line focus principle Reduce effective size of focal spot as far as heat capacity
Actual focal spot size to effective focal spot size Actual is smaller focal spot than effective
Anode angle and effective focal spot size Anode angle increases which means effective focal spot increases
What happens to anode heat capacity as anode angle increases Increased angle=increased heat capacity
What happens to field coverage as anode angle increases Increased angle=increased field coverage
What happens to resolution as anode angle increases Increased angle=decreased resolution
Anode heel effect More x rays on cathode side because x ray absorption in heel of anode
Spatial resolution on the anode side of the tube to the cathode side of the tube Resolution is greater in anode side
What is meant by extra focal or off focus radiation X rays that are created outside the focal spot
Vp/Vs=Np/Ns Is/Ip=Np/Ns if Ns is greater than Np that is a step up If Ns is less than Np it's step down
What is output voltage with 200 turns in primary coil and 100 in secondary if input voltage is 750V? Step up or step down Step down Vs=375 Ns<Np 750p/Vs=200p/100s
What is output voltage from transformer with 25 turns in primary coil and 75 turns in secondary if input voltage was 120V? Step up or step down Step up Vs=360 Ns>Np 120p/Vs=25p/75s
What is output amperage of transformer that has 100 turns in primary coil and 1000 in secondary if input current is 10 amps? Step up or step down 1 amp and step up Is/10p=100p/50s
Red light has wavelength of 650nm what is frequency? 3*10^8/6.5*10^-7=4.6*10^14
If an x ray photon has wavelength of 1.5nm what is frequency? 3*10^8/1.5*10^-9=2*10^17 s/s
Yellow light has frequency of 5.17*10^14 Hz what is its wavelength? 3*10^8m/s/5.17*10^14=5.8*10^-7
If an X-ray has frequency of 4*10^19Hz what is its wavelength? 3*10^8/4*10^19=7.5*10^-12
What is frequency of 85keV X-ray? 85*10^3/4.15*10^-15=20.48*10^18
What is energy contained in 45Mhz photon emitted during MR scan? (4.15*10^-15)(45*10^6)=1.8675*10^-7
What is energy of photon of red light that has a wavelength of 650nm? (4.15*10^-15)(3*10^8)/650*10^-9=1.91eV
What is energy of photon that has a wavelength of .1 nm? (4.15*10^-15)=(3*10^8)/.1*10^-9=12.4keV
Filament electron Projectile
L to K shell 69-12= 57
M to K shell 69-3=66
Double mA Twice as many x rays
Tube current How many electrons across tube
Inverse square law I1/I2=D^2 2/D^2 1 I1=100 rem I2=? D1=2ft D2=6ft 100/x=(6/2)^2=11.1
Intensity= Quantity
Transformer Increased voltage
Diode One way path for electricity use for rectification in x ray tube
Rectification Change AC to DC
Electrons Cathode to anode
Voltage ripple Different of peak voltage and lowest point of voltage Lower ripple more efficient x ray production
Transformer Needed to produce x rays so you need high voltage transformer to create voltage needed
Step up voltage increase Amps decrease
Step down voltage decrease Amps increase
Step up secondary More winding
Step down primary Has more windings
Diode Is a one way oath for electricity and is used for rectification
Rectification Changes AC to DC
Current travels Anode to cathode
Electrons travel Cathode to anode
Voltage ripple Max-min Max*100
Lower ripple More efficient x rays
Single phase ripple one pulse 100%
Single phase full wave 100% ripple
3 phase 6 pulse 13-25%
3 phase 12 pulse 3-10%
High frequency (constant potential) Has highest valve
EMR C=f/lambda 3*10^8
X radiation wave 10-10 to 10-14 Hz 10-18 to 10-22
Plancks constant 4.15*10^-15
Anode Creates heat by excitation, falls out of atom, back into the atom and then spits out energy
Outer shell Ionization
Characteristic radiation Produced by inner shell electron, ionized outer shell that falls down to fill it, higher energy to lower x ray is emitted, calculate energy x ray photon difference of binding that difference is the difference is the characteristic
Ionization occurs If it has more binding energy than what it collided with
Character radiation Is discrete but it's character of what's being ionized
Production of brems Electrons come attracted to positive nucleus and diverges/circles around and slows down, changes direction of energy given off by slowing down x ray photon
Brems Can be any strength and any energy in the incoming electron any or all can be a photon
If given tungsten You can tell if something is not characteristic but could still be brems
Energy range of brems Is considered continuous or discrete
Tuungsteb target needs 70 kvp to get ionization of k shell for useful x rays Can still get from other shells but not useful
Milliamperes increase Intensity not energy
Kilovoltage increases Average maximum quantity of the beam
Kvp Is amount of energy crossing the tube faster and harder which creates more x rays
Increase the Z number of the target You increase quantity/quality of the beam
Changing target material Is the only way to make radiation change
Generator ripple Less ripple higher effective energy and its clearer
Beam hardening Gets rid of low intensity and keeps intensity higher
To harden beam Filter it
Binding energy of m shell 2.5 keV but depends on element because the difference in atomic mass number is going to have an effect on binding energy
Discrete spectrum Every element has an exact amount of photons which are released called characteristic of that element
Continuous spectrum All colors are present and range from shirt to long wavelength
How many different energies can a tungsten characteristic x ray have 1 of 15
Visible light is describe by Wavelength
Radio waves are described by Frequency
AM radio ranges from 535-1705 kHz
FM ranges from 88-108MHz
MRI uses radio waves with frequency of 40-50 MHz
X rays are higher energy and shorter wavelength and have higher frequency than Visible light
EM acts like a wave and Particle
Photons are Discrete bundles of energy
Photon energy is directly proportional to Photon frequency