Radiation And The Atom

Question 1

The interaction of electromagnetic radiation can occur by what ways?

Answer 1

By scattering (change in trajectory), absorption (removal of radiation), or at very higher energies, transformation into particulate radiation (energy to mass conversion)

Question 2

What are the two ways of describing EM radiation?

Answer 2

As waves and as discrete particle-like packets or quanta of energy called photons.

Question 3

What characteristic is more apparent when EM radiation interacts with objects of similar dimensions as the photon’s wave length?

Answer 3

Wave characteristics

Question 4

These characteristics of EM radiation are more evident when an object’s dimensions are much smaller than the photon’s wavelength.

Answer 4

Particle characteristics

Question 5

The particle-like behaviour of x-rays is exemplified by the classical “billiard-ball” type of collision between an x-ray photon and an orbital electron during _______ event.

Answer 5

Compton scattering

Question 6

Wave characteristics

Any wave (EM or mechanical,such as sound) can be characterised by their ______, ______, _____, and ______.

Answer 6

Amplitude (maximal height)
Wavelength
Frequency
Period

Question 7

This is the intensity of the wave

Answer 7

Amplitude

Question 8

This is the distance between two identical points on adjacent cycles.

Answer 8

Wavelength

Question 9

The time required to complete one cycle of wave is the _____.

Answer 9

Period

Question 10

The number of periods that occur per second is the _______.

Answer 10

Frequency

Question 11

Because speed of EM radiation is constant in a given medium, it’s frequency and wavelength are ______ proportional.

Answer 11

Inversely

Question 12

Discrete (particle-like) packets (or quanta) of EM energy are called ______.

Answer 12

Photons

Question 13

Wavelength of x-rays and gamma rays are typically measured in fractions of _______.

Answer 13

Nanometer

1 nm = 10 to the negative 9 nm

Question 14

Frequency is expressed in _____.

Answer 14

Hertz (Hz)

Question 15

Energies of photons are commonly expressed in ______.

Answer 15

Electron volts (eV)

Question 16

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

Answer 16

One electron volt

Multiples of the eV common to medical imaging are the keV (1,000 eV) and the MeV (1,000,000 eV)

Question 17

An atom or molecule that has lost or gained one or more electrons has a net electrical charge and is called ______.

Answer 17

Ion

Question 18

In general, photons of higher frequency than the far UV region of the spectrum (wavelengths greater than 200 nm) have sufficient energy per photon to remove bound electrons from atomic shells, thereby producing ionized atoms or molecules.

Radiation in this portion of the spectrum is called?

Answer 18

Ionizing radiation

Question 19

EM radiation with photon energies in and below the UV region is called?

Answer 19

Nonionizing radiation

Question 20

What is ionization energy?

Answer 20

The minimum energies necessary to remove an electron

Question 21

This property of particulate radiation has a positive electrical charge and is identical to the nucleus of a hydrogen atom.

Answer 21

Protons

Protons are found in the nuclei of all atoms

Question 22

Electrons emitted by the nuclei of radioactive atoms are referred to as _______.

Answer 22

Beta particles

Except for their nuclear origin, negatively charged beta minus particles, or negatrons, are indistinguishable from ordinary orbital electrons

Question 23

These are positively charge electrons.

They are are form of antimatter that ultimately combines with matter in a unique transformation in which all of their mass is instantaneously converted to an equivalent amount of energy in the form of high-energy gamma rays.

Answer 23

Beta plus particles or positrons

Question 24

A ________ is an uncharted nuclear particle that has a mass slightly greater than that of a proton.

They are released by nuclear fission and are used for radionuclide production.

Answer 24

Neutron

Question 25

These particle consists of two protons and two neutrons; it thus has +2 charge and is identical to the nucleus of a helium atom.

They are emitted by many high atomic number radioactive elements, such as uranium, thorium, and radium.

Answer 25

Alpha particles

These particles emitted outside the bodyare harmless, alpha particles emitted inside the body cause more extensive cellular damage per unit energy deposited in tissue than any type of radiation used in medical imaging

Question 26

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

It is composed of an extremely dense positively charged nucleus, containing protons and neutrons, and an extra nuclear cloud of light negatively charged electrons.

Answer 26

Atom

Question 27

In its _______ state, an atom is electrically neutral number of protons equals the number of electrons.

Answer 27

Nonionized state

Question 28

The innermost shell of an atom, in which the electrons have the lowest energies.

Answer 28

K shell

Question 29

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

Answer 29

Valence shell

Question 30

It is the energy required to remove an orbital electron completely from the atom.

Answer 30

Orbital binding energy

Question 31

For radiation to be ionizing, the energy transferred to the electron must be ____________ its binding energy.

Answer 31

Equal or exceed

Question 32

Due to the closer proximity of the electrons to the positively charged nucleus, the binding energy of the K-shell is _______ than that of the outer shells.

Answer 32

Greater than

Question 33

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 _____?

Answer 33

Electron cascade

Question 34

Emissions from transitions exceeding 100 eV are called ______.

Answer 34

Characteristic or fluorescent x-rays

Characteristic x-rays are named according to the orbital in which vacancy occurred. Ex. K-characteristic x-ray)

Question 35

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 _______________.

Answer 35

Auger electron emission

In this case, the energy released is transferred to an orbital electron, typically the same shell as the cascading electron

The ejected Auger electron possesses kinetic energy equal to the difference between the transition energy and the binding energy of the ejected electron.

Question 36

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

Answer 36

Fluorescent yield

Question 37

The nucleus is composed of protons and neutrons, known collectively as _______.

Answer 37

Nucleons

Question 38

The number of protons in the nucleus is the _________ number, and the number of protons and neutrons within the nucleus is the ______ number.

Answer 38

Atomic number

Mass number

Question 39

The _______ force between the protons is repulsive and countered by the attractive force resulting from the exchange of gluons (subnuclear particles) among the nucleons.

Answer 39

Coulumbic force

The exchange forces, also called the strong force, hold the nucleus together but operate only very short (nuclear distances)

Question 40

The lowest energy state of a atomic nucleus is called the ______.

Answer 40

Ground state

Question 41

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

Answer 41

Excited state.

Question 42

Excited states that exist longer than 10 (-12) s are referred to as ________.

Answer 42

Meta stable or isomeric states

Question 43

Species of atoms characterized by the number of protons and neutrons and the energy content of the atomic nuclei are called _______.

Answer 43

Nuclides

Question 44

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

Answer 44

Radioactive

Radioactive decay (radioactive disintegration)

Question 45

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

Answer 45

Gamma ray

This energy transition is analogous to the emission of characteristic x-rays following electron transition

Question 46

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

Answer 46

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

Question 47

Nuclear de-excitation process does not always result in the emission of a gamma ray.

An alternative form of de-excitation is _______, in which the de-excitation energy is completely transferred to an orbital electron.

Answer 47

Internal conversion

Question 48

The energy required to separate an atom into its constituent parts is the _________.

It is the sum of the orbital electron binding energy and the nuclear binding energy.

Answer 48

Atomic binding energy

Question 49

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

Answer 49

Nuclear binding energy

Question 50

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 known as the _________.

Answer 50

Mass defect

Question 51

During nuclear fission, a nucleus with large atomic mass splits into two usually unequal parts called _________, each with an average binding energy per nucleon greater than that of the original nucleus.

Answer 51

Fission fragments