Medical physics Exam Test Questions with All
Correct Answers.
Describe the relationship between kinetic energy of electrons wavelength and energy of x
rays - Correct Answer-Ek = E - hc/wavelength ( E = energy of the x ray )
Describe x rays - Correct Answer-Em wave of High energy short wavelength , high
enough energyto ionise atoms and possess similar dangers to gamma waves
how does an xray tube work - Correct Answer-high voltage power supply ( 1000V)
connected to cathode where current heats filament which releases electrons. electrons
are accelerated by the pd towards target metal (anode), when electrons strike the target
and are rapidly decelerated x rays are emitted
what material is used for the target metal and why - Correct Answer-A heat-resistant block
of metal, usually Tungsten, is embedded at the end of the anode, facing the cathode
disadvantages of using an xray tube - Correct Answer-highly inefficient, only 1% of kinetic
energy is converted to xray energy
Define thermionic emission - Correct Answer-The emission of electrons from a heated
source
Why is it important that the anode and cathode are charged in the way are - Correct
Answer-Conventional current flows out of the cathode into the anode
What is simple scattering - Correct Answer-A low-energy X-ray photon encounters an
electron in an atom causing it to be scattered without a change in energy, during this
photons are deflected from their initial path by interaction
what is compton scattering - Correct Answer-incoming xray has enough energy to remove
electron. xray absorbed still some remaining energy so emitted by low energy photon
what is pair production - Correct Answer-incoming xray has a high enough energy and
interacts with the nucleus of an atom. an electron-positron pair is produced and they
normally annihilate and produce a pair of lower energy photons.
, what is a positron - Correct Answer-mass of an electron, positive charge
What is the photoelectric effect - Correct Answer-xray absorbed by electron, electron uses
energy to escape the atom, electron released with some kinetic energy ( hf = ∅ + Ke)
mass-energy equivalence equation - Correct Answer-e = mc²
Factors that affect x ray attenuation - Correct Answer-- density of material, intensities
before and after passing through the material, the amount of radiation the specific material
absorbs through the material
attentuation coefficient equation - Correct Answer-I = I₀e⁻(ˣµ^), µ = attenutation
coefficient, x = thickness
What is contrast media - Correct Answer-Substance with high attenuation coefficient,
produces more distinct images
Examples of contrast media - Correct Answer-Barium used to investigate the gastro-
intestinal system ( ingested ), Iodine to observe blood and fluid movement ( injected ).
why do certain contrast media work - Correct Answer-High nucleon and proton number
which increases the attenuation coefficient.
What is Bremstrahlung ( braking radiation ) ? - Correct Answer-x rays are produced by
braking radiation by charged particles due to their acceleration
what so the sharp k-lines in the xray spectra indicate - Correct Answer-caused by incident
electrons which remove electrons close to the nuclei in anode atoms. higher energy
electrons will then transition down to lower energy shell and excess energy will be emitted
as radiation
how to use xray spectra to estimate max accelerating p.d - Correct Answer-v = hc/eλ , use
minimum wavelength,
how will xray spectra graph change if accelerating p.d is increased - Correct Answer-
kinetic energy of electrons will increase, max energy of xrays will also increase, shortest
wavelength will decrease. k-lines higher but location stay same
Correct Answers.
Describe the relationship between kinetic energy of electrons wavelength and energy of x
rays - Correct Answer-Ek = E - hc/wavelength ( E = energy of the x ray )
Describe x rays - Correct Answer-Em wave of High energy short wavelength , high
enough energyto ionise atoms and possess similar dangers to gamma waves
how does an xray tube work - Correct Answer-high voltage power supply ( 1000V)
connected to cathode where current heats filament which releases electrons. electrons
are accelerated by the pd towards target metal (anode), when electrons strike the target
and are rapidly decelerated x rays are emitted
what material is used for the target metal and why - Correct Answer-A heat-resistant block
of metal, usually Tungsten, is embedded at the end of the anode, facing the cathode
disadvantages of using an xray tube - Correct Answer-highly inefficient, only 1% of kinetic
energy is converted to xray energy
Define thermionic emission - Correct Answer-The emission of electrons from a heated
source
Why is it important that the anode and cathode are charged in the way are - Correct
Answer-Conventional current flows out of the cathode into the anode
What is simple scattering - Correct Answer-A low-energy X-ray photon encounters an
electron in an atom causing it to be scattered without a change in energy, during this
photons are deflected from their initial path by interaction
what is compton scattering - Correct Answer-incoming xray has enough energy to remove
electron. xray absorbed still some remaining energy so emitted by low energy photon
what is pair production - Correct Answer-incoming xray has a high enough energy and
interacts with the nucleus of an atom. an electron-positron pair is produced and they
normally annihilate and produce a pair of lower energy photons.
, what is a positron - Correct Answer-mass of an electron, positive charge
What is the photoelectric effect - Correct Answer-xray absorbed by electron, electron uses
energy to escape the atom, electron released with some kinetic energy ( hf = ∅ + Ke)
mass-energy equivalence equation - Correct Answer-e = mc²
Factors that affect x ray attenuation - Correct Answer-- density of material, intensities
before and after passing through the material, the amount of radiation the specific material
absorbs through the material
attentuation coefficient equation - Correct Answer-I = I₀e⁻(ˣµ^), µ = attenutation
coefficient, x = thickness
What is contrast media - Correct Answer-Substance with high attenuation coefficient,
produces more distinct images
Examples of contrast media - Correct Answer-Barium used to investigate the gastro-
intestinal system ( ingested ), Iodine to observe blood and fluid movement ( injected ).
why do certain contrast media work - Correct Answer-High nucleon and proton number
which increases the attenuation coefficient.
What is Bremstrahlung ( braking radiation ) ? - Correct Answer-x rays are produced by
braking radiation by charged particles due to their acceleration
what so the sharp k-lines in the xray spectra indicate - Correct Answer-caused by incident
electrons which remove electrons close to the nuclei in anode atoms. higher energy
electrons will then transition down to lower energy shell and excess energy will be emitted
as radiation
how to use xray spectra to estimate max accelerating p.d - Correct Answer-v = hc/eλ , use
minimum wavelength,
how will xray spectra graph change if accelerating p.d is increased - Correct Answer-
kinetic energy of electrons will increase, max energy of xrays will also increase, shortest
wavelength will decrease. k-lines higher but location stay same
