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Physics exam 2
| Question | Answer |
|---|---|
| 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 |
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