Radiation Production and Characteristics – Comprehensive Review

These 150 question-and-answer flashcards cover the essential concepts, definitions, formulas, historical facts, and safety principles from the lecture transcript on Radiation Production and Characteristics. They span measurement systems, mechanics, atomic structure, forces, radioactivity, radiation types, x-ray generation, interaction with matter, radiologic units, photon theory, and radiological protection, providing a comprehensive study aid for exam preparation.

What are the three base quantities in physics?

Mass, length, and time.

Which system of units forms the basis of the modern SI?

The MKS system (meter, kilogram, second).

What is the SI unit for mass?

Kilogram (kg).

What physical object historically defined the kilogram?

A platinum-iridium cylinder stored at the International Bureau of Weights and Measures in Paris.

How is one meter currently defined?

The distance light travels in 1/299,792,458 second.

What is the standard unit of time?

Second (s).

Which clock is used for defining the second today?

The cesium-133 atomic clock.

Give an example of a secondary (derived) quantity.

Area, volume, velocity, density, etc.

Name four special quantities used in radiologic science.

Exposure, absorbed dose, effective dose, radioactivity.

What international organization stores the primary standards of mass, length, and time?

The International Bureau of Weights and Measures (BIPM) in Paris.

State Newton’s First Law of Motion.

A body remains at rest or moves in a straight line at constant velocity unless acted on by an external force (law of inertia).

Express Newton’s Second Law mathematically.

F = m a

What is the value of g (acceleration due to gravity) on Earth?

9.8 m/s².

Define momentum and give its formula.

Momentum is the product of mass and velocity: p = m v.

Define work and its SI unit.

Work = force × distance; measured in joule (J).

Define power and give its formula.

Power = work ÷ time (P = W/t); SI unit is watt (W).

State the law of conservation of energy.

Energy can neither be created nor destroyed, only transformed from one form to another.

Provide the equation for kinetic energy.

KE = ½ m v².

Provide the equation for gravitational potential energy.

PE = m g h.

Name the three methods of heat transfer.

Conduction, convection, and radiation.

Who proposed the plum-pudding model of the atom?

J. J. Thomson.

Which atomic model introduced the nucleus?

Rutherford’s nuclear model (1911).

Which atomic model is likened to a miniature solar system?

Bohr atom (1913).

What are the three fundamental subatomic particles?

Electron, proton, neutron.

How many electrons can the M-shell hold at maximum?

18 electrons (using 2 n²).

What is meant by atomic number (Z)?

The number of protons in the nucleus.

Define atomic mass number (A).

The total number of protons plus neutrons (nucleons) in the nucleus.

What are isotopes?

Atoms with the same atomic number but different mass numbers.

What term describes atoms with the same mass number but different atomic numbers?

Isobars.

Atoms with the same neutron number but different proton numbers are called what?

Isotones.

Define isomers in nuclear physics.

Atoms with identical Z and A that exist at different energy states (metastable).

List the four fundamental forces of nature.

Gravitational, electromagnetic, strong nuclear, weak nuclear.

Which fundamental force is the weakest?

Gravity.

Which force binds electrons to atoms?

Electromagnetic force.

Which force holds protons and neutrons together in the nucleus?

Strong nuclear force.

What type of radioactive decay converts a neutron into a proton and an electron?

Beta minus (β−) decay.

What particle is emitted during alpha decay?

A helium nucleus (2 protons + 2 neutrons).

What is gamma decay?

The emission of a high-energy photon (γ-ray) from an excited nucleus without change in Z or A.

Define half-life.

The time required for half the radioactive atoms in a sample to decay.

Write the radioactive decay law.

A = A₀ e^(−λt) where λ = 0.693/t½.

What is the half-life of Technetium-99m?

6 hours.

Differentiate irradiation from contamination.

Irradiation: exposure to radiation; Contamination: material becomes a radiation source itself.

List four natural sources of background radiation.

Cosmic rays, terrestrial radiation, internally deposited radionuclides (e.g., K-40), radon gas.

Name the largest natural contributor to background dose.

Radon.

Identify the chief man-made source of ionizing radiation.

Medical x-rays.

What are the two main categories of ionizing radiation?

Particulate radiation and electromagnetic radiation.

Give two examples of particulate ionizing radiation.

Alpha particles, beta particles (also electrons, positrons, neutrons, protons when energetic).

What is the speed of all electromagnetic radiation in vacuum?

3.0 × 10⁸ m/s (speed of light).

How do x-rays differ from gamma rays?

Only by origin: x-rays originate outside the nucleus; gamma rays originate inside the nucleus.

State the old unit and SI unit for exposure in air.

Old: roentgen (R); SI: coulomb per kilogram (C/kg).

Convert 1 Gy to rad.

1 Gy = 100 rad.

What SI unit replaces the rem?

Sievert (Sv).

Which SI unit measures radioactivity?

Becquerel (Bq).

Equation linking frequency and wavelength of EM radiation.

c = f λ (velocity = frequency × wavelength).

State Planck’s equation.

E = h f (energy equals Planck’s constant times frequency).

What does the inverse square law state for radiation intensity?

Intensity is inversely proportional to the square of the distance from the source (I₁/I₂ = d₂²/d₁²).

Who discovered x-rays and in what year?

Wilhelm Conrad Roentgen in 1895.

Name the first Nobel Prize winner in Physics for work with x-rays.

Wilhelm Roentgen (1901).

What device invented by Coolidge in 1913 revolutionized x-ray tubes?

The hot-cathode vacuum (Coolidge) tube.

What is thermionic emission?

Release of electrons from a heated filament in the x-ray tube.

Define space-charge effect.

Repulsion of additional electrons due to the cloud of electrons near the filament limiting further emission.

What are the two main interactions that produce diagnostic x-rays?

Characteristic radiation and bremsstrahlung radiation.

When does characteristic radiation occur?

When a projectile electron ejects an inner-shell electron and an outer-shell electron fills the vacancy.

Minimum tube potential needed to produce K-shell characteristic x-rays in tungsten.

Approximately 69 kVp.

Explain bremsstrahlung radiation.

X-rays produced when high-speed electrons are decelerated or ‘braked’ by the electric field of the nucleus.

How does increasing mA (or mAs) affect the x-ray emission spectrum?

Increases the amplitude (quantity) at all energies proportionally; shape remains unchanged.

Effect of increasing kVp on the x-ray spectrum.

Increases both quantity and quality (shift to higher energies and higher amplitude).

What does added filtration do to the x-ray beam?

Reduces quantity, increases average energy (‘hardens’ the beam).

Why is tungsten commonly used as anode target material?

High atomic number (74) for efficient x-ray production, high melting point, good thermal conductivity.

List the five interactions of x-rays with matter.

Coherent (classical) scatter, Compton scatter, photoelectric effect, pair production, photodisintegration.

Which two interactions dominate in diagnostic radiology?

Compton scattering and photoelectric effect.

What is Coherent (Thompson) scattering?

Elastic scattering of low-energy x-rays with no ionization and no energy loss, only change in direction.

Why is Compton scatter problematic in radiography?

It degrades image contrast and contributes to occupational dose.

How does Compton scatter vary with photon energy and atomic number?

Probability decreases slowly with increasing photon energy; essentially independent of atomic number.

Define photoelectric effect.

Total absorption of an x-ray by ejecting an inner-shell electron; photon disappears.

Photoelectric probability is proportional to what factors?

Approximately Z³/E³ (atomic number cubed over energy cubed).

What important phenomenon follows photoelectric interaction?

Emission of characteristic x-rays or Auger electrons from the atom.

Energy threshold for pair production.

1.02 MeV.

What happens during annihilation radiation?

A positron combines with an electron, converting their masses into two 0.511 MeV gamma photons.

At what photon energy does photodisintegration become possible?

Above about 10 MeV.

What is meant by beam hardening?

Raising average photon energy by adding filtration or high kVp, removing low-energy photons.

Why are double-emulsion films better than single-emulsion plates?

They reduce exposure time and improve image quality (Leonard, 1904).

Who invented the stationary grid to reduce scatter?

Gustav Bucky (1913).

What moving grid refinement is widely used?

Potter-Bucky grid (introduced 1921).

Define primary radiation.

The useful x-ray beam emitted directly from the tube before interacting with the patient.

Define remnant (exit) radiation.

Radiation that emerges from the patient to expose the image receptor.

What is off-focus (stem) radiation?

Photons produced outside the anode focal spot that can blur the image.

What is leakage radiation?

X-rays escaping the tube housing other than through the collimated window; limited to <1 mGy/hr at 1 m.

Equation for maximum electrons per shell (Pauli exclusion).

2 n², where n is the principal quantum number.

What rule limits outer shell to eight electrons?

Octet rule.

Type of bond formed by electron sharing.

Covalent bond.

Type of bond formed by electron transfer between atoms.

Ionic bond.

Type of bonding where electrons are delocalized among many atoms.

Metallic bonding.

What is a molecule?

A combination of two or more atoms bonded together.

Define compound.

A chemical substance composed of identical molecules of two or more elements.

Which decay mode involves K-shell electron capture by the nucleus?

Electron capture.

What is internal conversion?

Nucleus transfers excess energy to an orbital electron, ejecting it without emitting a γ-ray.

Which decay mode ejects a neutron from the nucleus?

Neutron emission.

Define spontaneous fission.

Heavy nucleus splits into two smaller nuclei plus neutrons without external cause.

What is an isomeric transition?

Metastable nucleus loses energy via γ-ray (or internal conversion) without changing Z or A.