RAD 102 exam 2

Which of the following best defines radiation?

A. Stored energy held within the nucleus of an atom
B. Emitted energy, usually transmitted by a particle
C. Energy that only travels through a physical medium
D. The removal of an electron from an atom

B. Emitted energy, usually transmitted by a particle

When radiation interacts with matter, energy is transferred from the particle to which of the following?

A. The nucleus of the target atoms
B. The electrons in the target atoms
C. The neutrons in the target atoms
D. Other incoming particles

B. The electrons in the target atoms

1. Energy transferred to an atom’s electrons can cause which two outcomes?

A. Ionization or excitation

B. Fission or fusion

C. Absorption or reflection

D. Decay or capture

A. Ionization or excitation

2. What is ionization potential (binding energy)?
A. Energy released when an electron joins an atom
B. Energy of the emitted photon
C. Energy needed to move an electron up one shell
D. Energy required to free an electron from the atom

D. Energy required to free an electron from the atom

3. Binding energy is higher when:
A. The electron is farther from the nucleus and Z is lower
B. The electron is farther from the nucleus and Z is higher
C. The electron is closer to the nucleus and Z is higher
D. The electron is closer to the nucleus and Z is lower

C. The electron is closer to the nucleus and Z is higher

4. Which process(es) move electrons?
A. Ionization only
B. Excitation only
C. Both ionization and excitation
D. Neither

C. Both ionization and excitation

5. Which process(es) leave a hole in the orbitals?
A. Ionization only
B. Excitation only
C. Both ionization and excitation
D. Neither

C. Both ionization and excitation

6. Which process leaves an electron at a higher energy level (still bound to the atom)?
A. Ionization
B. Excitation
C. Both
D. Neither

B. Excitation

7. How can an excited electron relax?
A. X-ray emission or Auger electron emission
B. Compton scatter or pair production
C. Alpha or beta decay
D. Fission or fragmentation

A.X-ray emission or Auger electron emission

8. What is the W value?
A. Total energy needed to ionize an atom
B. Average energy lost per ion pair created by a charged particle
C. Energy lost per unit distance traveled
D. Minimum energy for excitation

B. Average energy lost per ion pair created by a charged particle

9. The two types of radiation interactions are:

A. Elastic and inelastic
B. Primary and secondary
C. Directly and indirectly ionizing
D. Coulomb and nuclear

C. Directly and indirectly ionizing

10. Which statement correctly describes directly vs. indirectly ionizing radiation?
A. Direct = charged particles ; indirect = neutral particles (photons and neutrons)
B. Direct = neutral particles (photons and neutrons); indirect = charged particles
C. Direct = photons; indirect = electrons
D. Direct = alphas only; indirect = everything else

A. Direct = charged particles ; indirect = neutral particles (photons and neutrons)

11. How does indirectly ionizing radiation transfer energy to the medium?
A. It transfers energy directly to the medium
B. It creates a secondary particle, which then transfers energy to the medium
C. It transfers energy only to the nucleus
D. It doesn’t transfer energy

B. It creates a secondary particle, which then transfers energy to the medium

13. In a Coulomb interaction, energy is lost by the ______ particle and gained by the ______.
A. incident; electrons
B. electrons; incident
C. incident; nucleus
D. secondary; incident

A. incident; electrons

12. How do charged particles interact with matter?
A. Through magnetic attraction
B. Through Coulomb interactions
C. Through gravitational pull
D. Through nuclear binding

B. Through Coulomb interactions

Charged particles transfer energy to the electrons of a medium by which mechanism?

A. Nuclear fission
B. Coulomb collisions
C. Photoelectric absorption
D. Magnetic induction

B. Coulomb collisions

In a Coulomb (electrostatic) collision, a moving projectile interacts with a stationary target. What happens to the kinetic energy (KE) of each?

A. The target gains KE and the projectile gains KE
B. The target loses KE and the projectile gains KE
C. The target gains KE and the projectile loses KE
D. The target loses KE and the projectile loses KE

C. The target gains KE and the projectile loses KE

When electrons in a medium gain energy from a passing charged particle, what can result?

A. Fission or fusion
B. Ionization or excitation
C. Pair production or annihilation
D. Absorption or reflection

B. Ionization or excitation

Question 13. In a Coulomb interaction, energy is lost by the ______ particle and gained by the ______.
A. incident; electrons
B. electrons; incident
C. incident; nucleus
D. secondary; incident

A. incident; electrons

In Coulomb interactions, what is conserved?
A. Energy only
B. Charge only
C. Energy and momentum
D. Mass and volume

C. Energy and momentum

Why are protons and alphas called “heavy” charged particles?
A. They have a higher charge than electrons
B. They are about 2000 times more massive than an electron
C. They move faster than electrons
D. They only interact with nuclei

B. They are about 2000 times more massive than an electron

How much energy does a heavy particle lose in a single collision?
A. A large fraction of its energy
B. About half
C. Very little, so many collisions are needed
D. All of it

C. Very little, so many collisions are needed

Stopping power is defined as:
A. The total distance a particle travels before stopping
B. Average energy lost per unit pathlength
C. Energy lost per ion pair
D. The maximum energy in one collision

B. Average energy lost per unit pathlength

Stopping power increases with ______ and decreases with ______.
A. velocity; Z
B.density; Z
C. Z; particle mass
D. Z; velocity squared

D. Z; velocity squared

What causes the Bragg peak?
A. The particle speeds up near the end of its path
B. The target density suddenly increases
C. Energy loss drops as the particle slows
D. The particle slows, which increases energy loss, which slows it more, and so on

D. The particle slows, which increases energy loss, which slows it more, and so on

Range depends on:
A. Particle energy only
B. Target color and temperature
C. Particle energy and size, plus target density and Z
D. Pathlength only

C. Particle energy and size, plus target density and Z

What is the approximate range of an alpha particle?
A. Air: a few inches; tissue: microns
B. Air: several meters; tissue: centimeters
C. Air: a few inches; tissue: several centimeters
D. Air: microns; tissue: a few inches

A. Air: a few inches; tissue: microns

Why is an alpha emitter harmless outside the body but dangerous inside?
A. Alphas are stopped by the dead layer of the epidermis or a sheet of paper, but inside the body they give up energy quickly in sensitive tissue
B. Alphas penetrate deeply outside the body but not inside
C. Alphas only interact with air
D. Alphas lose less energy inside the body

A. Alphas are stopped by the dead layer of the epidermis or a sheet of paper, but inside the body they give up energy quickly in sensitive tissue

What happens to an alpha particle as it slows?
A. Energy loss decreases, so it passes through tissue
B. Energy loss rises (Bragg peak), then it picks up electrons from target atoms
C. It splits into two protons
D. It speeds up and escapes

B. Energy loss rises (Bragg peak), then it picks up electrons from target atoms

What are “light” charged particles, and how does their mass compare to the target electrons they hit?

A. Protons or alphas, which are much heavier than the target electrons
B. Electrons or positrons, which have the same mass as the target electrons (0.511 MeV/c²)
C. Electrons or positrons, which are about 2000 times lighter than the target electrons
D. Neutrons or photons, which have no mass

B. Electrons or positrons, which have the same mass as the target electrons (0.511 MeV/c²)

How does the collision physics of light charged particles differ from that of heavy charged particles?

A. They lose very little energy per collision and need many collisions
B. They never change direction
C. They can lose up to 100% of their energy in a single collision, so they need fewer collisions but change direction a lot
D. They lose exactly 0.2% of their energy per collision

C. They can lose up to 100% of their energy in a single collision, so they need fewer collisions but change direction a lot

What is bremsstrahlung?

A. Radiation emitted when a charged particle is deflected in a strong electric field, producing x-rays
B. Radiation emitted when an electron drops to a lower shell
C. The ejection of an outer electron by an incoming photon
D. The annihilation of an electron and a positron

A. Radiation emitted when a charged particle is deflected in a strong electric field, producing x-rays

In what two ways do electrons lose energy as they pass through matter?

A. Collisions and bremsstrahlung (radiation)
B. Fission and fusion
C. Absorption and reflection
D. Coulomb collisions and nuclear decay

A. Collisions and bremsstrahlung (radiation)

In what way do heavy charged particles lose energy as they pass through matter?

A. Annihilation
B. Bremsstrahlung only
C. Collisions and bremsstrahlung equally
D. Collisions only

D. Collisions only

Which statement about the practical range of beta particles (electrons) is correct?

A. Range in air is a few inches, and they pose no risk outside the body
B. Range in air is a few feet (about 10 ft per MeV), and range in tissue is mm to cm
C. Range in air is several hundred feet, and range in tissue is several meters
D. Range in air is microns, and range in tissue is nanometers

B. Range in air is a few feet (about 10 ft per MeV), and range in tissue is mm to cm

Why don’t electrons show a distinct Bragg peak the way heavy charged particles do?

A. Electrons lose less energy per collision than heavy particles
B. Electrons lose large amounts of energy per collision and scatter at random angles, so energy loss averages out across many particles
C. Electrons are neutral, so they don’t ionize
D. Electrons stop immediately at the surface

B. Electrons lose large amounts of energy per collision and scatter at random angles, so energy loss averages out across many particles

What happens when electrons and positrons slow down?

A. Electrons react chemically with atoms in the target, while positrons annihilate with an electron to produce photons
B. Both undergo annihilation
C. Electrons annihilate, while positrons react chemically with atoms
D. Both are absorbed by the nucleus

A. Electrons react chemically with atoms in the target, while positrons annihilate with an electron to produce photons

In a collision that produces a delta ray, what happens to the energy transferred to the target material?

A. The electron is ejected with excess kinetic energy (ionization)
B. The electron moves to a higher energy level but stays in the atom
C. The nucleus absorbs the energy and becomes unstable
D. The energy is released immediately as a photon

A. The electron is ejected with excess kinetic energy (ionization)

Delta rays behave just like which other type of radiation?

A. Alpha particles
B. Beta particles
C. Gamma rays
D. Neutrons

B. Beta particles

What is Linear Energy Transfer (LET)?

A. The total distance a particle travels before stopping
B. Energy absorbed by the target material per unit distance
C. Average energy lost per ion pair created
D. The maximum energy a particle can transfer in one collision

B. Energy absorbed by the target material per unit distance

Which particles are high-LET radiation, and why does that matter?

A. Alphas, protons, neutrons, and heavy ions. They deposit energy densely, so they are more damaging.
B. Photons and electrons. They deposit energy sparsely, so they are more damaging.
C. Alphas and protons only. They penetrate deeply, so they are more damaging.
D. Gamma rays and x-rays. They are neutral, so they are more damaging.

A. Alphas, protons, neutrons, and heavy ions. They deposit energy densely, so they are more damaging.

Which of the following are low-LET radiations?

A. Alphas, protons, and heavy ions
B. Beta particles, gamma rays, and x-rays
C. Neutrons and alphas
D. Heavy ions and neutrons

B. Beta particles, gamma rays, and x-rays

What is specific ionization (SI), and how is it calculated?

A. Ions produced per unit distance, SI = LET / W
B. Energy lost per ion pair, SI = LET × W
C. Energy absorbed per unit distance, SI = W / LET
D. Total ions produced by one particle, SI = range × W

A. Ions produced per unit distance, SI = LET / W

Energy transferred by Coulomb interactions occurs through which two mechanisms?

A. Fission and fusion
B. Collisions and bremsstrahlung
C. Absorption and reflection
D. Annihilation and decay

B. Collisions and bremsstrahlung

Why do neutral particles (photons and neutrons) interact less often with matter than charged particles do?

A. They are too heavy to interact
B. They have no charge, so there is no Coulomb force and interactions are less likely
C. They are absorbed by the nucleus every time
D. They carry too much energy to interact

B. They have no charge, so there is no Coulomb force and interactions are less likely

What is a photon?

A. A heavy charged particle that carries electric charge
B. A negatively charged particle with a mass of 0.511 MeV/c²
C. A neutral particle found in the nucleus
D. A particle of light used to describe its particle behavior, where energy is inversely related to wavelength

D. A particle of light used to describe its particle behavior, where energy is inversely related to wavelength

How do photons transfer energy to matter?

A. They ionize atoms directly through Coulomb collisions along their whole path
B. They transfer energy only to the nucleus
C. They interact with an atom or electron and transfer energy to an electron (a delta ray), which then deposits energy just like a beta particle
D. They lose energy gradually through many small collisions, like alphas

C. They interact with an atom or electron and transfer energy to an electron (a delta ray), which then deposits energy just like a beta particle

Which set lists the four photon interaction mechanisms, whose likelihood depends on photon energy?

A. Photoelectric effect, Compton scattering, pair production, photonuclear
B. Photoelectric effect, bremsstrahlung, annihilation, Coulomb collisions
C. Compton scattering, delta rays, pair production, fission
D. Photoelectric effect, Compton scattering, bremsstrahlung, photonuclear

A. Photoelectric effect, Compton scattering, pair production, photonuclear

What happens in the photoelectric effect?

A. The photon scatters off an electron and continues with less energy
B. The photon is absorbed and an electron is ejected with the photon’s energy minus the electron’s binding energy
C. The photon creates an electron-positron pair
D. The photon is absorbed by the nucleus, which then emits a particle

B. The photon is absorbed and an electron is ejected with the photon’s energy minus the electron’s binding energy

In the photoelectric effect, how is the photon’s energy transferred, and where is it most likely to occur?

A. Half the energy goes to the electron and half is re-emitted as a lower-energy photon
B. All the energy goes to the electron, and it is most likely with an outer-shell electron
C. All the energy goes to the electron except what is needed to overcome its binding energy, and it is most likely with an inner-shell electron
D. The energy goes to the nucleus, and it is most likely with the innermost proton

C. All the energy goes to the electron except what is needed to overcome its binding energy, and it is most likely with an inner-shell electron

Which statement correctly describes the probability of the photoelectric effect?

A. It is most likely at high gamma energies and is independent of Z
B. It increases with photon energy and decreases with Z
C. It is most likely at low gamma energies, decreases as photon energy increases, increases with Z of the target, and spikes sharply near characteristic x-ray energies (absorption edges)
D. It depends only on electron density, not on Z or energy

C. It is most likely at low gamma energies, decreases as photon energy increases, increases with Z of the target, and spikes sharply near characteristic x-ray energies (absorption edges)

What happens in Compton scattering?

A. The photon is completely absorbed and an electron is ejected
B. The photon collides with an electron and transfers some of its energy (minus the binding energy), then continues in a different direction with less energy
C. The photon converts into an electron-positron pair
D. The photon is absorbed by the nucleus, which then emits a particle

B. The photon collides with an electron and transfers some of its energy (minus the binding energy), then continues in a different direction with less energy

In Compton scattering, what happens to the incident photon and to the electron?

A. The photon is absorbed; the electron is excited
B. The photon is scattered with more energy; the electron is absorbed
C. The photon is ionized; the electron is scattered
D. The photon is scattered; the electron is ionized and carries away the lost energy minus the binding energy

D. The photon is scattered; the electron is ionized and carries away the lost energy minus the binding energy

Which statement correctly describes the probability of Compton scattering?
A. Depends strongly on Z of the target and increases with photon energy
B. Directly dependent on electron density, independent of Z, and inversely dependent on photon energy
C. Independent of electron density and directly dependent on Z
D. Directly dependent on photon energy and inversely dependent on electron density

B. Directly dependent on electron density, independent of Z, and inversely dependent on photon energy

In low-energy (coherent) scattering, there is no change in which two quantities?

A. Wavelength and energy
B. Charge and mass
C. Direction and wavelength
D. Momentum and charge

A. Wavelength and energy

Low-energy (coherent) scattering occurs for photon energies below about:

A. 10 keV
B. 100 keV
C. 1 MeV
D. 10 MeV

A. 10 keV

Low-energy (coherent) scattering contributes to what in imaging, and what is its effect in therapy?

A. It improves image contrast and increases therapeutic dose
B. It adds background “fog” to images and has no impact in therapy
C. It has no effect on imaging but is the main source of therapeutic dose
D. It creates the image signal and reduces dose in therapy

B. It adds background “fog” to images and has no impact in therapy

Which three processes are types of coherent scattering?

A. Rayleigh, Mie, and Thomson scattering
B. Compton, Rayleigh, and Mie scattering
C. Rayleigh, Thomson, and photoelectric scattering
D. Mie, Compton, and Thomson scattering

A. Rayleigh, Mie, and Thomson scattering

What is pair production, and what is the minimum photon energy required?

A. A photon scatters off an electron and creates a second photon, and it requires E > 1.022 MeV
B. A photon is converted into an electron and a positron, and it requires E > 511 keV
C. A photon is converted into an electron and a positron, and it requires E > 1.022 MeV
D. A photon is absorbed by the nucleus and emits a neutron, and it requires E > 10 MeV

C. A photon is converted into an electron and a positron, and it requires E > 1.022 MeV

In pair production, where does the energy above the 1.022 MeV threshold go?

A. It is emitted as a second photon
B. It is lost as bremsstrahlung
C. It is absorbed by the nucleus as heat
D. It becomes kinetic energy of the electron and positron

D. It becomes kinetic energy of the electron and positron