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Physics > AIM: Ch 2: Radiation and the Atom > Flashcards

AIM: Ch 2: Radiation and the Atom Flashcards

1
Q

It is energy that travels through space or matter.

A

Radiation

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2
Q

Two categories of radiation of importance in medical imaging are:

A

Electromagnetic and particulate

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3
Q

T/F: EM radiation has no mass, is unaffected by either electric or magnetic fields, and has a constant speed in a given medium.

A

True

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4
Q

Maximal speed of EM radiation

A

2.998 x 10^8 m/s

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5
Q

The interaction of EM radiation can occur by:
1. Change in trajectory:
2. Removal of the radiation:
3. At very higher energies, energy to mass conversion:

A
  1. Scattering
  2. Absorption
  3. Transformation into particulate radiation
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6
Q

Name the form of EM radiation used for the following modalities:
1. Nuclear imaging
2. Radiography, fluoroscopy and mammography

A
  1. Gamma rays
  2. X-rays
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7
Q

It is a discrete particle-like packets or quanta of energy

A

Photons

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8
Q

____ characteristics are more apparent when EM radiation interacts with objects of similar dimensions as the photon’s wavelength.

A

Wave

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9
Q

Particle characteristics of EM radiation, on the other hand, are more evident when an object’s dimensions are much ____ than the photon’s wavelength.

A

Smaller

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10
Q

It is the intensity of the wave

A

Amplitude

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11
Q

It is the distance between any two identical points on adjacent cycles.

A

Wavelength

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12
Q

The time required to complete one cycle of a wave is the ____

A

Period

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13
Q

Number of periods that occur per second

A

Frequency

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14
Q

It is the temporal shift of one wave with respect to the other

A

Phase

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15
Q

It is defined as the energy acquired by an electron as it traverses an electrical potential difference (voltage) of one volt in a vacuum.

A

1 eV

Energies of photons are commonly expressed in electron volts (eV)

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16
Q

What region of the radiation spectrum serves as the landmark that separates ionizing radiation from non-ionizing radiation?

A

UV region

Ionizing radiation: wavelengths >200 nm

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17
Q

What wavelength will have sufficient energy to cause ionizing radiation?

A

> 200 nm

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18
Q

The minimum energy necessary to remove an electron

A

Ionizing energy

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19
Q

Ionizing energy for water

A

11.2 eV

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20
Q

The average energy expended per ion pair (W) for water and tissue equivalent gas:

A

30 W

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21
Q

Electrons emitted by the nuclei of radioactive atoms

A

Beta particles

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22
Q

Of nuclear origin, negatively charged beta-minus particles are also called ____

A

Negatrons

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23
Q

Positively charged electrons

A

Positrons

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24
Q

A neutron is an uncharged nuclear particle that has a mass slightly ____ than that of a proton.

A

Greater

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25
Q

Which particle has the greatest elementary charge, rest mass and energy equivalent?

A

Alpha

26
Q

Neutrons are released by nuclear ____ and are used for radionuclide production

A

Fission

27
Q

It is a common unit of mass used in atomic and nuclear physics, defined as 1/12th of the mass of an atom of 12C.

A

Atomic mass unit (amu)

One amu is equivalent to 931.5 MeV of energy.

28
Q

It is the smallest division of an element in which the chemical identity of the element is maintained.

A

Atom

29
Q

The outer electron shell of an atom, which determines the chemical properties of the element.

A

Valence shell

30
Q

The energy required to remove an orbital electron completely from the atom

A

Orbital binding energy

31
Q

What is the formula by which you can compute the highest number of electrons each shell can contain?

A

2n^2

32
Q

T/F: For a particular electron shell, binding energy also increases with the number of protons in the nucleus (i.e., atomic number).

A

True

33
Q

When an electron is removed from its shell by an x-ray or gamma ray photon or a charged particle interaction, a vacancy is created in that shell. This vacancy is usually filled by an electron from an outer shell, leaving a vacancy in the outer shell that in turn may be filled by an electron transition from a more distant shell. This series of transitions is called what?

A

Electron cascade

34
Q

The energy released by each transition is equal to the difference in binding energy between the original and final shells of the electron. This energy may be released by the atom as ____ or ____

A

Characteristic x-rays or Auger electrons

35
Q

Emissions from transitions exceeding 100 eV are called ____

A

Characteristic or fluorescent x-rays.

36
Q

An electron cascade does not always result in the production of a characteristic x–ray or x-rays. A competing process that predominates in low Z elements is ____

A

Auger electron emission

37
Q

The probability that the electron transition will result in the emission of a characteristic x-ray is called ____

A

Fluorescent yield (w)

38
Q

It is the probability that the transition will result in the ejection of an Auger electron.

A

1-w

39
Q

Auger emission predominates in ____ Z elements and in electron transitions of the outer shells of heavy elements.

A

Low

40
Q

Nucleons = ____ + ____

A

Protons + Neutrons

41
Q

Atomic number

A

Number of protons in the nucleus

42
Q

Mass number

A

Protons + Neutrons

43
Q

Atomic mass

A

Actual mass of the atom

44
Q

Subnuclear particles are also known as

A

Gluons

45
Q

The lowest energy state of an atomic nucleus

A

Ground state

46
Q

Nuclei with energy in excess of the ground state are said to be in an

A

Excited state

The average lifetimes of excited states range from 10^-16 s to more than 100 y

47
Q

Excited states that exist longer than 10^-12 s are referred to as

A

Metastable or isomeric states

48
Q

Nuclides with the same:
1. Z
2. A
3. A-Z
4. Atomic and mass numbers but different energy states in the nucleus

A
  1. IsotoPes
  2. IsobArs
  3. IsotoNes
  4. Isomers
49
Q

On a plot of Z versus N, these stable nuclides fall along a “line of stability” for which the N/Z ratio is approximately ____ for low Z nuclides and approximately ____ for high Z nuclides

A

1, 1.5

50
Q

Nuclides that decay (i.e., transform) to more stable nuclei are said to be ____, and the transformation process itself is called ____

A

radioactive, radioactive decay (radioactive disintegration)

51
Q

The EM radiation emitted from the nucleus as the excited state transitions to a lower (more stable) energy state is called a

A

Gamma ray

52
Q

When this nuclear de-excitation process takes place in an isomer (e.g., Tc-99m), it is called ____

A

Isomeric transition

53
Q

T/F: In isomeric transition, the nuclear energy state is reduced with decrease in A or Z.

A

False

In isomeric transition, the nuclear energy state is reduced with no change in A or Z

54
Q

This process occurs when de-excitation energy is completely transferred to an orbital (typically K, L, or M shell) electron

A

Internal conversion

55
Q

The energy required to separate an atom into its constituent parts is called

A

Atomic binding energy

56
Q

Energy necessary to disassociate a nucleus into its constituent parts and is the result of the strong forces acting between nucleons.

A

Nuclear binding energy

57
Q

T/F: The total energy of the bound particles is less than that of the separated free particles.

A

True

58
Q

The binding energy can be calculated by subtracting the mass of the atom from the total mass of its constituent protons, neutrons, and electrons; this mass difference is called the ____

A

Mass defect

59
Q

During nuclear fission, a nucleus with a large atomic mass splits into two usually unequal parts called fission fragments, each with an average binding energy per nucleon ____ than that of the original nucleus. In this reaction, the total nuclear binding energy ____.

A

Greater, increases

60
Q

Number of neutrons per cm2/s

A

Neutron flux

Physics (16 decks)

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