physics 3 Flashcards
what is an x-ray?
- defined as weightless packages of pure energy
- without electrical charge
- travel in waves along a straight line
- specific frequency and speed
properties of x-rays
- v short wavelength
- have no mass
- unaffected by electric/magnetic fields
- travel in speed of light in vacuum
- travels in straight lines
- causes ionisation
what are the 2 types of events that can lead to x-ray production?
An electron travelling at high speed may experience a sudden change in direction or motion
An electron in an atom may undergo a transition from a high energy state to a low energy state
which type of event is more common? where?
first, in x-ray production in tube
what is the production process in x-rays?
- negative cathode produces electrons
- positive anode is electron target
there is energy conversion
- potential type
- kinetic type
- kinective energy proportional to potential difference
what are the types of energy conversion in production process of x-rays?
there is energy conversion
- potential type
- kinetic type
- kinective energy proportional to potential difference
what happens when the exposure button is depressed?
- cathode becomes strongly neg
- anode strongly pos
electrons emitted from filament exist within strong electric field
large measure of pd potential energy
- potential energy changed into kinetic energy until electrons reach anode, accelerating very high speed
what does slide 7 graph show?
radiation intensity in relation to energy, and the noticeable characteristic radiation ‘peaks’ as they have higher intensity than brems.
label the graph
you got this bro!!!
What is bremsstrahlung radiation step by step
- incident e- from cathode hits target anode
- e- passes close to nucleus of tungsten atom
- charge from photon in nucleus attracts e- changing direction of e-
- causes deceleration releasing energy in form of x-ray
what is more blue or red in bremsstrahlung photon energy?
red is more common
explain bremsstrahlung photon energies
two electrons from filament
blue: close to nucleus, deviate and convert some kinetic energy to x-ray photon
- photon has more energy (shorter wavelength)
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explain bremsstrahlung photon energy ranges
diagnostic energy range 30-120kVp (more bremsstrahlung)
below 70kVp, tungsten target, 100% bremsstrahlung
above 70kVp - then its 85% bremsstrahlung
what is the continuous spectrum? and graph look at on ur own!
- represents the intensity of x-rays being distributed in a continuous fashion over the range of wavelengths present.
- short wavelength limit
- photons of minimum wavelength have maximum energy
what is the graph on slide 11?
unfiltered Bremsstrahlung spectrum shows a ramp-shaped relationship between the number and energy of the x-rays produced, with the highest x-ray energy determined by the peak voltage (kVp) applied across the tube
A typical filtered Bremsstrahlung spectrum shows no x-ray output below around 10keV
what is characteristic radiation protection?
- filament e- collides with e- within an atom of the target
- if filament e- energy greater than binding energy of e- in the shell, it will eject the e-
- this causes release of energy in the form of a photon
- outer shell e- will move to fill vacancy, releasing lower energy photons
compare bremsstrahlung and characteristic interactions
- no diference, simply produced by different processes
- majority of interactions produced at diagnostic voltages are bremsstrahlung
what is characteristic cascade? where is it?
in characteristic radiation protection
When vacancies on the shell are filled
will trigger a characteristic cascade when electrons ‘cascade’ from the outer shells to the innermost shells until all vacancies are filled.
bremstrahllung and characteristic have what?
discrete energies that are confined to that element
tungsten sum characteristic x-ray energy
EK-shell – EL-shell
= 69.5keV – 10.2keV
= 59.3keV
explain graph on slide 15th: Filtered Bremsstrahlung & Characteristic Radiation of Tungsten
seeee!!!
