Fundamentals of Physics and Medical Imaging
WEEK 11 – THE ATOM, QUANTA AND IONISING RADIATION
Mass-Energy Equivalence
The physical principle that a measured quantity of energy is equivalent to a measured quantity of mass. The equivalence is expressed by Einstein’s equation E = mc2, where E represents energy, m the equivalent mass, and c the speed of light.
Radioactivity
Radioactivity refers to the particles emitted from nuclei due to nuclear instability. Because the nucleus experiences the intense conflict between the two strongest forces in nature, it should not be surprising that many nuclear isotopes are unstable and emit some radiation.
Strong Nuclear Force
Acts between all nucleons. Strongly attractive at a specific range of inter-particle distance but repulsive at very short distances.
Nuclear Binding Energy
Nuclear binding energy is the energy required to separate an atomic nucleus completely into its constituent protons and neutrons or, equivalently, the energy liberated by combining individual protons and neutrons into a single nucleus.
Radioactive (Nuclear) Decay
Radioactive decay, also known as nuclear decay or radioactivity, is the spontaneous breaking down of a nucleus accompanied by the emission of radiation.
Nucleon
A nucleon is one of the particles that makes up the atomic nucleus. Each atomic nucleus consists of one or more nucleons, and each atom consists of a cluster of nucleons surrounded by one or more electrons.
Isotope
An isotope is a specific version of a nucleus in terms of the number of protons and neutrons.
Radioisotope
A radioisotope is an unstable isotope. It has an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached.
Nuclide
A nuclide, also called a nuclear species, is a species of atom characterized by the number of protons, the number of neutrons, and the energy state of the nucleus.
Radionuclide
A radionuclide (radioactive nuclide, radioisotope, or radioactive isotope) is an atom with excess nuclear energy, making it unstable. This excess energy can create and emit radiation from the nucleus.
Alpha Particle
An alpha particle consists of 2 protons and 2 neutrons. It has a mass of 4 amu and the most mass by far of the emissions. It always has kinetic energy when emitted.
Beta Particle
Two forms of beta particles exist:
- Negatron (β-): Identical in charge and mass to an electron.
- Positron (β+): Has the same mass but the opposite charge of an electron.
Both types have very low mass (0 amu) and high kinetic energy when emitted.
Gamma Ray
- Gamma is just EM energy – no mass, no charge.
- It is normally emitted in conjunction with particulate emission (usually shortly after).
- It is due to a change in the binding energies of nucleons.
- Gamma emission itself does not alter the number of protons or neutrons.
Half-Life
Each specific nuclide has a characteristic timing of decay. HALF LIFE is the time for half of the nuclei in a sample of a specific nuclide to decay.
Activity
‘Activity’ is the number of decays per unit time occurring in a sample of radioactive material.
- SI unit is the Becquerel = 1 decay per second.
Transmutation
Transmutation is the conversion of one chemical element into another. Decay often involves changing one particle type into another. Decay may also involve emitting protons and neutrons. If any of those happen, the number of protons in the nucleus changes, so not only does the nuclide change, but the atom becomes a different element!
- This is a ‘transmutation’.
WEEK 10 – LIGHT AND OPTICS
Wavefront
A wavefront is a set of waves traveling together, radiating spherically from a point. The result is a series of parallel lines. All points on a wavefront can be considered a source of waves of that same frequency and wavelength.
Normal
A line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line.
Angle of Incidence
The angle between the incident ray and the normal.
Angle of Reflection
The angle between the reflected ray and the normal.
Specular Reflection
Reflection of smooth surfaces such as mirrors or a calm body of water leads to specular reflection.
Diffuse Reflection
Reflection off rough surfaces such as clothing, paper, and asphalt roadways leads to diffuse reflection.
Virtual Image
Virtual images are formed in locations where light does not actually reach.
Real Image
Real images are formed on the same side of the mirror as the object, and light passes through the image location.
Lens
A lens is a carefully ground or molded piece of transparent material that refracts light rays to form an image.
Convex
Convex mirrors were silvered on the outside of the sphere and minify images.
Concave
Concave mirrors were silvered on the inside of the sphere and magnify images.
Convergent (Converging) Lens
Designed to cause individual rays or waves to come together to a point after leaving the lens.
Divergent (Diverging) Lens
Designed to cause individual rays or waves to move farther apart after leaving the lens.
Index of Refraction
The index of refraction (n) of a material is the ratio of the speed of light in a vacuum to the speed of light in that material.
Total Internal Reflection
Total internal reflection is the reflection of the total amount of incident light at the boundary between two media.
Critical Angle
The critical angle is the angle of incidence at which 100% reflection occurs (total internal reflection).
Coherent Light
Coherent wave sources, such as lasers, produce monochromatic light. This means that each wave has the same frequency or wavelength. Each wave also has the same amplitude and is in phase with one another.
Laser
Light Amplified Stimulated Emission of Radiation.
WEEK 9 – ELECTROMAGNETIC ENERGY
Radiation
Radiation is the transport of energy in waves or particles through space or a material medium.
Electromagnetic Energy
Electromagnetic energy is the transport of energy through space as a disturbance of electrical and magnetic waves.
Electromagnetic
The vibrating electric and magnetic fields regenerate each other to make up an EM wave.
Spectrum
A spectrum is a complete range of variations of a phenomenon.
Electron Binding Force & Electron Binding Energy
- Electron binding energy is a measure of the energy required to free electrons from their atomic orbits.
- Binding energy is measured in electronvolts (eV) since it measures the energy required to move an electron through a potential difference.
Electronvolt
An electronvolt is the quantity of energy required to move one electron through a potential difference of one volt.
Excitation
Excitation occurs when an orbital electron receives a quantity of energy equal to the energy for an allowable location change (ΔE). An excited electron will move to a higher energy level.
De-Excitation
- Electrons don’t stay in an excited state and will ‘jump’ down to a lower level very quickly.
- An electron must give up ΔE to return to its original energy level and orbital level.
Ionisation
Ionisation is the energy necessary to release an electron from the neutral atom. It is sufficient energy to ionize an atom by collision with an orbital electron.
Transparent
Transparent means NO energy was removed from the wave during passage through matter.
- The wave passes through without loss of intensity.
Opaque
Opaque means all energy is absorbed by the matter.
Quantum
Since the quantity of energy within a photon is specific, the photon may also be called a ‘quantum’.
Photon
A pulse of EM is a discrete packet of energy called a photon.
Penetrability
WEEK 8 – ELECTROMAGNETISM
Magnetic Force
Attraction or repulsion arises between electrically charged particles because of their motion.
Magnetic Pole
Magnetic poles are the points of origin of magnetic forces.
Magnetic Field
Magnetic fields are zones where magnetic lines of force are in effect.
Magnetism
Magnetism is produced by the motion of charges, resulting in forces of attraction and repulsion.
Magnetic Field Intensity
Magnetic field intensity is a vector quantity. Its magnitude is the strength of a magnetic field at a point in the direction of the magnetic field at that point.
Magnetic Domain
The magnetic field of an individual iron atom is so strong that interactions among adjacent atoms cause large clusters to line up. These clusters of aligned atoms are called magnetic domains.
Ferromagnetism
Ferromagnetism is the property of certain materials that enables them to form magnets and be attracted to magnets.
Retentivity (or Remanance)
Retentivity is the ability of a substance to retain or resist magnetization, frequently measured as the strength of the magnetic field that remains in a sample after removing an inducing field.
- “Iron is easily magnetized but has low retentivity.”
Permeability
Permeability measures the resistance encountered when forming a magnetic field in a classical vacuum.
Permanent Magnet
Permanent magnets hold a net magnetic field on their own.
- Must be ferromagnetic.
Electromagnet
An electromagnet is a piece of metal that becomes magnetic when an electric current is passed through or near it.
Solenoid
A solenoid is a coil of wire carrying a current.
Electric Motor
Electric motors involve rotating coils of wire driven by the magnetic force exerted by a magnetic field on an electric current. They transform electrical energy into mechanical energy.
Electromagnetic Induction
Electromagnetic induction is a process of inducing voltage by changing the magnetic field in loops of wire.
Faraday’s Law
The EMF induced in a circuit is proportional to the time rate of change of the magnetic flux linking that circuit.
Electromagnetism
Electromagnetism is a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually shows electromagnetic fields, such as electric fields, magnetic fields, and light.
Flux
Flux is the number of field lines passing through a surface of a magnetic field.
Flux Linkage
- Flux linkage requires the relative motion to be non-parallel.
- Crossing the conductor with field lines; imagine the flux line cutting through the wire.
Generator
A generator is a device that converts mechanical energy to electrical energy. A loop of wire is placed within a strong stationary magnetic field.
Motor Effect
When charge moves along the wire, there is a perpendicular upward force on the charge. Since there is no conducting path upward, the force on the charge tugs the wire upward.
Generator Effect
When a wire with no initial current is moved downward, the charge in the wire experiences a deflecting force perpendicular to its motion. There is a conducting path in this direction, so the charge moves, constituting a current.
Transformer
A transformer converts AC from one voltage to another. It makes use of Faraday’s law and the ferromagnetic properties of an iron core to efficiently raise or lower AC voltages.
- Two coils of wire (primary and secondary); EMF source for the primary coil.
WEEK 7 – PRACTICAL CIRCUITS AND ELECTRICAL SAFETY
Series Circuit
A circuit contains multiple devices connected in series (one after another).
Parallel Circuit
A circuit contains multiple devices connected in parallel (on a different path).
Switch
A switch is a device used for making and breaking electric current through the circuit.
Direct Current
DC is the flowing of charges in one direction.
Alternating Current
AC is the flow of electric charge that periodically reverses direction.
Circuit Rating
The current received by an electric component or device operating under normal conditions.
Circuit Overload
If the current drawn by all devices connected in a circuit is more than the maximum current rating for the given circuit, the condition is called overloading.
Fuse
A fuse is a circuit-limiting device (CLD) that opens the circuit by destroying its conducting path. The device has a conducting path with a low melting point.
Circuit Breaker
A circuit breaker is a CLD that opens the circuit by moving two contacts apart when the maximum allowable current level is exceeded. The separation of contacts opens the circuit loop, stopping the flow of current.
Class I Device
Class 1 equipment relies for its safety upon a satisfactory means of earthing from the equipment to the circuit protective conductors of the fixed installation.
Class II Device
Class 2 equipment is also commonly known as “double insulated.” As there is no earth required for Class 2 equipment, there is no reliance on the earthing of the fixed installation for their safety.
Leakage Current
The current flows through the protective ground conductor to ground.
Short Circuit
A short circuit is a very low resistance conducting path to ground. This is normally due to a faulty connection that is either bypassing the normal resistance path or creating a parallel path to it.
Residual Current Device (RCD)
An RCD is a circuit-monitoring device. It operates on the principle that normal circuit operation has equal current magnitude in active and neutral wires.
Equipotential Earthing
Electric Shock
The passing of current through the body.
Electrocution
Macroshock
Macroshock is an electric shock due to current flow into the body via the skin. Current flows through a large quantity of tissue, so the current to the heart is only a small portion of what entered the body (about 5%).
Microshock
Microshock is a current resulting from a direct electrical connection to the heart muscle.
WEEK 6 – ELECTROSTATICS & ELECTRODYNAMICS
Net Charge
An unbalance of charge (a different number of electrons and protons, positive/negative net charge).
Ion
A particle with a net charge is called an ion.
Ionization
The process of causing an atom or molecule to have an imbalance of charge is called ionization.
Induction
Induction charging charges an object without actually touching the object to any other charged object.
Coulomb
The SI unit of charge.
Conductor
Conductors are materials that permit electrons to flow freely from particle to particle.
Insulator
Insulators are materials that impede the free flow of electrons from atom to atom and molecule to molecule.
Semiconductor
A semiconductor is a material with the ability to conduct electricity that varies depending on the conditions.
Grounding (Earthing)
Connect an object to the ground and discharge the object (remove the net charge).
Charge Polarization
Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field.
Electric Dipole
An electric dipole is two charged objects, with equal but opposite electric charges, separated by a distance.
Electric Field
An electric field is a zone where electric force is in effect.
Electric Potential Energy
Electric potential energy is the energy a charge has due to its position relative to other charges.
Electrical Potential
Electrical potential is the amount of work needed to move a unit charge from a reference point to a specific point against an electric field.
Volt
The SI unit of electrical potential (Electrical potential = energy/charge).
Potential Difference (Voltage)
The difference in electrical potentials between two locations (voltage drop).
Electromotive Force (EMF)
EMF is a potential rise. An EMF source provides the net fields to give electrons a flow direction and energy. Energy is added to the charges as they move between locations.
Battery
A battery is a device that converts chemical energy to electrical energy.
Electric Current
The quantity of charge flowing past a point in the conducting path per unit time. I = q/t.
Ampere
The SI unit of electric current.
Conduction Electrons
A conduction electron is an electron in the conduction band of a solid, where it is free to move under the influence of an electric field.
Ohmic Resistance
Ohmic resistance is the category of opposition to the flow of current in a circuit that results in heating of the conductor.
Ohm
The SI unit of Ohmic resistance.
Electric Circuit
A circuit is a loop path for the movement of electrical energy from a source to a user using the flow of charge.
WEEK 5 – SOUND
Sound
Sound is a pressure disturbance traveling through a medium. It originates from the vibration of an object that disturbs the medium surrounding it.
Reflection
Reflection of sound is called an echo. The amount of reflection depends on the dissimilarity of the two media.
Refraction
Refraction is a change in the direction of a wave as it passes from one medium to another.
Energy Wave Transmission
Sound is mechanical energy. When particles are compressed or rarefied, the energy is released as kinetic and transferred to neighboring particles by collisions.
Energy Wave Absorption
- Sound is pressure energy. Absorption is transferring wave energy to the medium through which it moves. The result is less energy staying with the pressure wave.
- The higher the absorption percentage, the lower the percentage of wave energy transmitted.
Natural Frequency
Each object tends to vibrate at a specific frequency when a pulse of energy is added to it.
Resonance
When the frequency of incoming pulsed energy matches the natural frequency of an object, the object’s amplitude of vibration increases greatly.
Sound Intensity
Sound intensity is an objective measure of the quantity of sound. It is the quantity of energy per unit time passing through an area. The greater the energy, the greater the displacement of the particles by the wave.
Intensity Level
- Intensity = Power/area.
- Intensity level is the logarithmic measure of relative intensity (decibel).
Decibel
1 decibel = 0.1 bel; 10 dB = 1 bel.
Energy
Energy is the ability to do work. Energy = Power * time.
Power
Power is the quantity of work done per unit time.
- Power = Work / time; Power = Intensity * area.
Amplitude
Amplitude is the magnitude of maximum displacement from equilibrium. Crest/Trough to resting position.
Doppler Effect
Whenever there is relative motion between the sender and receiver of sound, there is a frequency shift in the sound.
Doppler Shift
A Doppler shift is a change in frequency due to the Doppler effect.
WEEK 4 – GASES, HEAT AND TEMPERATURE, WAVES
Atmospheric Pressure
The earth’s atmosphere is the collection of gas molecules that make up the air. The air has weight, and it presses against everything it touches. That pressure is called atmospheric pressure or air pressure.
Temperature
We perceive the effect of the kinetic energy of molecules as warmth. The relative measure of that warmth is temperature.
Absolute Zero
Absolute zero is the lowest possible energy situation; no translational kinetic energy is present.
- Absolute zero = 0° K = -273° C
Heat
Heat is the quantity of energy transferred from a warmer object (higher temperature) to a cooler object (lower temperature). Heat is energy moving across a temperature gradient.
Internal Energy (Thermal Energy)
The sum of all forms of kinetic energy plus potential energy within an object is its ‘internal energy’.
Specific Heat Capacity
Specific heat capacity (c) is the quantity of heat (Q) required to change the temperature (T) of a unit mass (m) of a substance by 1 degree. ΔT = Q/(cm).
Thermal Expansion
Thermal expansion is the relative quantity of expansion of the object’s volume for a given rise in temperature.
Heat Conduction
- Conduction involves direct collisions between electrons of adjacent molecules.
- The collision transfers the energy from molecule to molecule.
- Conduction requires the close proximity of molecules.
Convection
- Convection involves the movement of molecules across a temperature gradient.
- This requires mobile molecules, so it occurs in fluids only, not solids.
Radiation
- Radiant energy is energy transported through space as waves.
- Heat radiation is electromagnetic (EM) energy waves.
Vibration
Vibration is a back-and-forth motion that occurs about an equilibrium point.
Wave
A wave is a periodic displacement relative to a baseline or equilibrium position that travels through space.
Periodic Motion
Periodic motion is motion repeated in equal intervals of time.
Period
A period is the time needed for one complete cycle of vibration to pass a given point, the time duration of one cycle.
Frequency
Frequency is the reciprocal of the period.
Amplitude
Amplitude is the magnitude of maximum displacement from equilibrium (Crest/trough to resting position).
Displacement
Wavelength
The wavelength is the distance from crest to crest (or from trough to trough).
Phase
Phase is the position of the wave at a point in time of its cycle.
Intensity
Intensity is the average power transfer over one period of the wave.
Wave Propagation
Wave propagation is the movement of waves. The disturbance is ‘kept alive’ as it moves through space.
Wave Speed (Velocity)
Wave speed is the distance traveled by a given point on the wave (such as a crest) in a given interval of time.
Transverse Wave
In a transverse wave, the direction of the disturbance is perpendicular to the direction of propagation.
Longitudinal Wave
In a longitudinal wave, the disturbance is along the same plane as the direction of propagation.
Compression
Compression is the increased density of the medium.
Rarefaction
Rarefaction is the decreased density of the medium.
Constructive Interference
- The disturbances must be in the same direction (both crests or both troughs).
- The result is increased amplitude that is the sum of the two amplitudes.
Destructive Interference
- The disturbances are in opposite directions (one crest, one trough).
- The result is decreased amplitude that is the sum of the two amplitudes.
WEEK 3 – STATES OF MATTER, PRESSURE AND FLUID BEHAVIOURS
Atom
An atom is the smallest particle into which an element can be divided without losing its chemical identity. The atom is the smallest identifiable unit of an element.
Nucleus
The nucleus is the small, dense region consisting of protons and neutrons at the center of an atom.
Proton
A proton is a positively charged particle that resides within the atomic nucleus.
Neutron
A neutron is a subatomic particle contained in the atomic nucleus. It has no net electric charge.
Electron
An electron is a very small particle of matter that has a negative charge of electricity and travels around the nucleus of an atom (travels in orbitals).
Element
An element is a material comprised entirely of one type of atom (all having the same number of protons). It can’t be broken down into any simpler substance.
Atomic Number
The atomic number is the number of protons in an atom.
Atomic Mass Number
The atomic mass number is the total number of neutrons and protons in the nucleus.
Ion
An ion is an atom or group of atoms that has an electric charge.
Isotope
Different atoms of a chemical element in the periodic table all have the same number of protons but may have a different number of neutrons in their nuclei. These different versions of the same element are called isotopes.
Compound
- Compounds consist of atoms of two or more different elements bound together.
- Compounds have chemical properties different from each constituent.
- The only way to break up a compound is to use chemical means.
Mixture
Mixtures are combinations of different elements but without chemical bonding between the different elements.
Molecule
A molecule is a group of two or more atoms bound together with shared electrons and has no net charge.
Volume
Volume is the measure of the 3D space occupied by an object.
Density
Density is the mass per unit volume of a material.
Elasticity
Elasticity is the relative quantity of temporary change to an object’s shape that occurs in response to the application of a deforming force to it. When the force is removed, the object’s shape is restored.
Tension
Tension describes the pulling force exerted by each end of a string, cable, or chain.
Compression
Compression is the pushing forces to different points on a material or structure.
Solid
- A solid maintains a fixed volume and shape regardless of its container.
- It changes shape only when broken or cut.
- Component particles are close together.
Liquid
- A liquid is nearly incompressible.
- It maintains a relatively fixed volume regardless of pressure but has a variable shape that adapts to its container.
- Component particles are close together but move freely relative to one another.
Gas
- A gas takes the volume and shape of its container.
- Component particles are relatively far apart and move freely relative to one another with virtually no inter-molecular interactions.
Fluid
All fluids can flow and have an indefinite shape. That would include both gases and liquids.
Pressure
- P = F / A
- Pressure is the ratio of the quantity of force exerted to the area over which it is distributed.
Volume Flow Rate
- F = Av
- Volume flow rate is the quantity of fluid that passes through a cross-sectional area of the path per unit time.
Laminar Flow
- Laminar flow is in regular layers.
- Little energy is removed from the system due to minimal friction.
Turbulent Flow
- Turbulent flow is chaotic flow.
- Increased energy is removed from the system due to friction, generating heat.
- Turbulence causes a reduced flow rate relative to applied pressure.
WEEK 2 – FORCE AND ENERGY
Inertia
Inertia refers to an object’s resistance to change in its motion. Maintaining a ‘state of motion’ could include maintaining a steady velocity, not just being stationary.
Force
Force is an influence that tends to change the state of motion of an object.
Net Force
Net force is the sum of all individual applied forces.
Mechanical Equilibrium
Mechanical equilibrium means the net force is zero.
Equilibrium Rule
Friction
Friction is an opposing or resistive force to the applied force causing motion.
Mass
Mass is the quantity of matter in an object.
Weight
Weight is the force on an object due to gravity.
Momentum
Momentum is the inertia of motion.
Impulse
Impulse is the change in momentum.
Work
- W = Fd
- Work (W) is the product of the force (F) on an object and the distance (d) through which the object is moved by that force.
Power
- P = W / t
- Power is the quantity of work done per unit time.
Energy
Energy is the ability to do work (Joules).
Mechanical Energy
Mechanical energy is the energy due to an object’s movement and relative position.
Potential Energy
Potential energy is energy due to relative position. When an object has work done on it to put it in a certain position relative to another location, the object stores that energy as ‘potential energy’.
Kinetic Energy
Kinetic energy is the energy of motion. Kinetic energy is the work an object can do while being brought to rest.
Centre of Mass
The center of mass is the point where all the mass of the object is concentrated.
Centre of Gravity
The center of gravity is a point from which the weight of a body or system may be considered to act. In uniform gravity, it is the same as the center of mass.
Stability
The position of the center of gravity of an object affects its stability. The lower the center of gravity (G), the more stable the object.
WEEK 1 – INTRODUCTION AND FUNDAMENTALS
Accuracy
The number of significant figures quoted in a result should represent the accuracy of the result.
Precision
The smallest order of 10 used in the expression of the number indicates the precision. For the level of precision, look for the number of decimal places.
Margin of Error
The margin of error is understood to be one-half of the size of the last significant place.
Significant Digits
The number of digits quoted in a measurement or result indicates how accurate the number is.
Scientific Notation
Scientific notation is an efficient and unambiguous way to express the number of significant figures and the order of magnitude of a numerical result.
Proportional Relationship
A proportional relationship exists when the causative variable’s magnitude impacts the dependent variable’s magnitude predictably.
Dependent Variable
The affected variable is termed dependent.
Independent Variable
The causative variable is termed independent.
Distance
Distance is the length between two locations following the actual path used to connect those two locations.
Displacement
Displacement is the length between two locations measured along a straight line to connect those locations.
Speed
Speed = distance / time.
Velocity
Velocity is speed in a specific direction.
Acceleration
Acceleration is the time rate of change in velocity.
Free Fall
Any object acted upon only by the force of gravity is said to be in free fall.
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