# Glossary

## Our Dynamic Universe

Our Dynamic Universe

### Distance

Distance

### Scalar quantity - How far the object actually moved

Scalar quantity - How far the object actually moved

### Displacement

Displacement

### Vector quantity - How far is the End point from the Start

Vector quantity - How far is the End point from the Start

### Speed

Speed

### Scalar quantity - Distance / Time

Scalar quantity - Distance / Time

### Velocity

Velocity

### Vector quantity - Displacement / Time

Vector quantity - Displacement / Time

### Angular Velocity

Angular Velocity

### The Rate of change of Angular displacement

The Rate of change of Angular displacement

### Tangential Velocity

Tangential Velocity

### The Linear Velocity of an object traveling in a circle. It is the velocity with which the object would move if the Centripetal Force was removed.

The Linear Velocity of an object traveling in a circle. It is the velocity with which the object would move if the Centripetal Force was removed.

### Acceleration

Acceleration

### "The Rate of Change of Velocity" or the "Change in Velocity per second"

"The Rate of Change of Velocity" or the "Change in Velocity per second"

### Angular Acceleration

Angular Acceleration

### The Rate of Change of Angular Velocity.

The Rate of Change of Angular Velocity.

### Radial Acceleration

Radial Acceleration

### The Acceleration towards the Center of a Circular motion, caused by a Centripetal Force.

The Acceleration towards the Center of a Circular motion, caused by a Centripetal Force.

### Centripetal Force

Centripetal Force

### Force inwards towards the Centre of a Circular motion.

Force inwards towards the Centre of a Circular motion.

### Newton's First Law

Newton's First Law

### An object will remain at rest or travel with a constant Velocity unless acted on by an unbalanced Force

An object will remain at rest or travel with a constant Velocity unless acted on by an unbalanced Force

### Newton's Second Law

Newton's Second Law

### The acceleration of an object is directly proportional to the unbalanced force and inversely proportional to its mass

The acceleration of an object is directly proportional to the unbalanced force and inversely proportional to its mass

### or

or

### F = ma

F = ma

### Newton's Third Law

Newton's Third Law

### If A exerts a force on B, then B exerts an equal but opposite force on A

If A exerts a force on B, then B exerts an equal but opposite force on A

### Torque

Torque

### The Turning Effect of a Force at a set distance from a pivot point, measured in Nm.

The Turning Effect of a Force at a set distance from a pivot point, measured in Nm.

### Law of Conservation of Energy

Law of Conservation of Energy

### Energy can not be created or destroyed, only changed from one form into another

Energy can not be created or destroyed, only changed from one form into another

### Law of Conservation of Momentum

Law of Conservation of Momentum

### In a collision where no external forces act, the total momentum before = the total momentum after

In a collision where no external forces act, the total momentum before = the total momentum after

### Angular Momentum

Angular Momentum

### The product of the angular velocity of a rotating object and its moment of Inertia, measured in kgm^{2}s^{-1}.

The product of the angular velocity of a rotating object and its moment of Inertia, measured in kgm

^{2}s

^{-1}.

### Law of Conservation of Angular Momentum

Law of Conservation of Angular Momentum

### In a collision where no external Torques act, the total angular momentum before = total angular momentum after.

In a collision where no external Torques act, the total angular momentum before = total angular momentum after.

### Elastic Collision

Elastic Collision

### Both Momentum and Kinetic energy are conserved

Both Momentum and Kinetic energy are conserved

### Inelastic Collision

Inelastic Collision

### Momentum is conserved, Kinetic Energy is NOT conserved

Momentum is conserved, Kinetic Energy is NOT conserved

### Low Earth Orbit

Low Earth Orbit

### Orbital Period ~ 90 Minutes

Orbital Period ~ 90 Minutes

### Mainly Used for Earth Observation Satellites

Mainly Used for Earth Observation Satellites

### Geostationary Orbit

Geostationary Orbit

### Orbital Period = 1 day

Orbital Period = 1 day

### For an Observer on the Earth, a Geostationary Satellite will appear stationary in the sky.

For an Observer on the Earth, a Geostationary Satellite will appear stationary in the sky.

### Gravitational Field Strength

Gravitational Field Strength

### The Force exerted upon a mass of 1 kg at a certain point within a Gravitational Field

The Force exerted upon a mass of 1 kg at a certain point within a Gravitational Field

### Gravitational Potential

Gravitational Potential

### The Work Done by an external Force to bring a Unit Mass from infinity to that point.

The Work Done by an external Force to bring a Unit Mass from infinity to that point.

### Gravitational Lensing

Gravitational Lensing

### The bending of Light around a massive object, caused by the light following a straight path through Curved Space-Time

The bending of Light around a massive object, caused by the light following a straight path through Curved Space-Time

### Escape Velocity

Escape Velocity

### The Minimum velocity required for an object to escape ( to infinity ) the Gravitational field of another object.

The Minimum velocity required for an object to escape ( to infinity ) the Gravitational field of another object.

### Schwarzschild Radius

Schwarzschild Radius

### The Distance from the centre of a Black hole at which the Escape Velocity is equal to the Speed of Light. Also known as the Event Horizon

The Distance from the centre of a Black hole at which the Escape Velocity is equal to the Speed of Light. Also known as the Event Horizon

### Singularity

Singularity

### A 1-dimensional point of infinite density at the centre of a Black Hole

A 1-dimensional point of infinite density at the centre of a Black Hole

### Time Dilation

Time Dilation

### ( Special Rel )

( Special Rel )

### The apparent increase in the length of 1 Second, caused by relative motion greater than 0.1 C. The consequence of this is that Time appears to run slower at relativistic speeds.

The apparent increase in the length of 1 Second, caused by relative motion greater than 0.1 C. The consequence of this is that Time appears to run slower at relativistic speeds.

### Time Dilation

Time Dilation

### ( General Rel )

( General Rel )

### The apparent increase in the length of 1 second, caused by the proximity of an object with a large gravitational field strength.

The apparent increase in the length of 1 second, caused by the proximity of an object with a large gravitational field strength.

### Length Contraction

Length Contraction

### The apparent decrease in the length of 1 meter, caused by relative motion greater than 0.1 C. The Consequence of this is that objects appear shorter ( in the direction of travel) at relativistic speeds

The apparent decrease in the length of 1 meter, caused by relative motion greater than 0.1 C. The Consequence of this is that objects appear shorter ( in the direction of travel) at relativistic speeds

### Worldline

Worldline

### The Line on a Space-Time diagram showing an object's position within Space-Time.

The Line on a Space-Time diagram showing an object's position within Space-Time.

### Protostar

Protostar

### Cloud of Dust and Gas collapsing under Gravity, increasing in Temperature and Pressure ( No Fusion ) .

Cloud of Dust and Gas collapsing under Gravity, increasing in Temperature and Pressure ( No Fusion ) .

### Main-Sequence Star

Main-Sequence Star

### Star held in Gravitational Equilibrium, Inwards Gravitational Force balanced by the Outwards Thermal Pressure due to Hydrogen Fusion.

Star held in Gravitational Equilibrium, Inwards Gravitational Force balanced by the Outwards Thermal Pressure due to Hydrogen Fusion.

### Post Main-Sequence Star

Post Main-Sequence Star

### Hydrogen Fusion ends, final fate of the Star dependent on its original Mass.

Hydrogen Fusion ends, final fate of the Star dependent on its original Mass.

### Black Body Object

Black Body Object

### An object which perfectly absorbs and emits all frequencies of Electromagnetic radiation.

An object which perfectly absorbs and emits all frequencies of Electromagnetic radiation.

### Luminosity

Luminosity

### The Total Power a Star emits across all frequencies

The Total Power a Star emits across all frequencies

### Doppler Effect

Doppler Effect

### Apparent change in the frequency of a Wave due to relative motion

Apparent change in the frequency of a Wave due to relative motion

### Red Shift

Red Shift

### Source Moving Away from Observer, Wavelength appears longer

Source Moving Away from Observer, Wavelength appears longer

### Blue Shift

Blue Shift

### Source Moving Towards the Observer, Wavelength appears shorter

Source Moving Towards the Observer, Wavelength appears shorter

### Cosmic Microwave Background

Cosmic Microwave Background

### The observed background radiation that is present in every direction in the Universe, it provides strong evidence of the Big Bang

The observed background radiation that is present in every direction in the Universe, it provides strong evidence of the Big Bang

### Dark Energy

Dark Energy

### Proposed type of Energy, used to account for the increasing rate of expansion of the Universe.

Proposed type of Energy, used to account for the increasing rate of expansion of the Universe.

### Dark Matter

Dark Matter

### Proposed type of Matter, used to account for "missing mass" within the Universe, it cannot be detected by conventional telescopes

Proposed type of Matter, used to account for "missing mass" within the Universe, it cannot be detected by conventional telescopes

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## Electricity

Electricity

### Potential Difference ( V )

Potential Difference ( V )

### Work done in transferring one coulomb of charge from one point to another

Work done in transferring one coulomb of charge from one point to another

### Current

Current

### Rate of Flow of Charge, measured in Amperes

Rate of Flow of Charge, measured in Amperes

### Current

Current

### ( Electron Flow )

( Electron Flow )

### Current Direction used in Scotland, shows the flow of Negative Charge Carriers moving from Negative to Positive

Current Direction used in Scotland, shows the flow of Negative Charge Carriers moving from Negative to Positive

### Current

Current

### ( Conventional )

( Conventional )

### Current Direction used in rest of World + Engineering in Scotland, shows the flow of Charge Carriers from Positive to Negative.

Current Direction used in rest of World + Engineering in Scotland, shows the flow of Charge Carriers from Positive to Negative.

### EMF

EMF

### The Energy given to each Coulomb of Charge passing through a Cell.

The Energy given to each Coulomb of Charge passing through a Cell.

### Internal Resistance

Internal Resistance

### The resistance of the Cell itself. A Cell can be modelled as a source of EMF in series with an internal Resistor

The resistance of the Cell itself. A Cell can be modelled as a source of EMF in series with an internal Resistor

### Lost Volts

Lost Volts

### Energy used (by the internal resistance of a battery) by each coulomb of charge passing through the Cell

Energy used (by the internal resistance of a battery) by each coulomb of charge passing through the Cell

### Terminal Potential Difference

Terminal Potential Difference

### The Voltage of a Cell or Battery as Measured across its terminals

The Voltage of a Cell or Battery as Measured across its terminals

### Direct Current

Direct Current

### Current ( and Voltage ) are in one direction only. An example of a DC supply is a Battery

Current ( and Voltage ) are in one direction only. An example of a DC supply is a Battery

### Alternating Current

Alternating Current

### Current ( and Voltage ) continuously change direction. An example of an AC supply is Mains Electricity

Current ( and Voltage ) continuously change direction. An example of an AC supply is Mains Electricity

### Peak Voltage or Current

Peak Voltage or Current

### The highest value reached by an Alternating Voltage or Current

The highest value reached by an Alternating Voltage or Current

### RMS Voltage or Current

RMS Voltage or Current

### The Average value of an Alternating Voltage or Current, causes heating equivalent to the DC Voltage or Current

The Average value of an Alternating Voltage or Current, causes heating equivalent to the DC Voltage or Current

### Electric Field Strength

Electric Field Strength

### Force applied to unit charge (1 coulomb) in an electric field

Force applied to unit charge (1 coulomb) in an electric field

### Coulomb's Law

Coulomb's Law

### The Electrostatic Force between two point charges is proportional to the product of the two Charges, and inversely proportional to the square of the distance between them.

The Electrostatic Force between two point charges is proportional to the product of the two Charges, and inversely proportional to the square of the distance between them.

### Electric Potential

Electric Potential

### The Work Done to move a Unit Positive Charge from Infinity to a point within an Electric Field.

The Work Done to move a Unit Positive Charge from Infinity to a point within an Electric Field.

### Capacitance

Capacitance

### ( F )

( F )

### The Number of Coulombs of charge stored per Volt

The Number of Coulombs of charge stored per Volt

### Time Constant

Time Constant

### The Time Taken for a Capacitor to Charge to 63% of Full Charge, or Discharge to 37% of Full Charge. Can be found by the product of the Capacitance and the Resistance within the Circuit.

The Time Taken for a Capacitor to Charge to 63% of Full Charge, or Discharge to 37% of Full Charge. Can be found by the product of the Capacitance and the Resistance within the Circuit.

### Capacitive Reactance

Capacitive Reactance

### The Opposition to Current Flow in a circuit due to a Capacitor, measured in Ohms.

The Opposition to Current Flow in a circuit due to a Capacitor, measured in Ohms.

### Magnetic Domain

Magnetic Domain

### A Region within a Ferromagnetic material where all atoms are aligned with their Magnetic Fields parallel to each other.

A Region within a Ferromagnetic material where all atoms are aligned with their Magnetic Fields parallel to each other.

### Induced EMF

Induced EMF

### The EMF generated in a conductor by a changing external Magnetic Field. The Induced EMF always acts to oppose the change which caused it, and therefore is also known as the Back EMF.

The EMF generated in a conductor by a changing external Magnetic Field. The Induced EMF always acts to oppose the change which caused it, and therefore is also known as the Back EMF.

### Electromagnetic Induction

Electromagnetic Induction

### The magnitude of the EMF produced is proportional to the rate of change of Magnetic Flux through the circuit.

The magnitude of the EMF produced is proportional to the rate of change of Magnetic Flux through the circuit.

### Self Inductance

Self Inductance

### The generation of a Back EMF within a Coil due to the current flowing within it.

The generation of a Back EMF within a Coil due to the current flowing within it.

### Electron-Volt

Electron-Volt

### Equal to 1.6 x10^{-19} J. Defined as the Work Done to move a single Electron through a Potential Difference of 1 Volt.

Equal to 1.6 x10

^{-19}J. Defined as the Work Done to move a single Electron through a Potential Difference of 1 Volt.

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## Particles and Waves

Particles and Waves

### Baryon

Baryon

### A Particle made of Three Quarks

A Particle made of Three Quarks

### Meson

Meson

### A Particle made of Two Quarks ( Quark - Anti Quark Pair )

A Particle made of Two Quarks ( Quark - Anti Quark Pair )

### Lepton

Lepton

### A Fundamental Particle of Matter

A Fundamental Particle of Matter

### Boson

Boson

### A Force Mediating Particle

A Force Mediating Particle

### Anti-Matter

Anti-Matter

### Every particle has an anti-particle. These are identical in every way, but carry the opposite charge. If they meet, they annihilate each other releasing Energy.

Every particle has an anti-particle. These are identical in every way, but carry the opposite charge. If they meet, they annihilate each other releasing Energy.

### Atomic Number

Atomic Number

### The Number of Protons within the Nucleus of an Atom.

The Number of Protons within the Nucleus of an Atom.

### Mass Number

Mass Number

### The Number of Nuclear Particles ( Protons + Neutrons ) within the Nucleus of an Atom.

The Number of Nuclear Particles ( Protons + Neutrons ) within the Nucleus of an Atom.

### Alpha Decay

Alpha Decay

### Radioactive Emission of an Alpha Particle ( consisting of a Helium Nucleus ) from the Nucleus of an Atom.

Radioactive Emission of an Alpha Particle ( consisting of a Helium Nucleus ) from the Nucleus of an Atom.

### Alpha Decay decreases the Mass Number by 4 and the Atomic Number by 2.

Alpha Decay decreases the Mass Number by 4 and the Atomic Number by 2.

### Beta Decay

Beta Decay

### Radioactive Emission of a Beta Particle ( consisting of a High Energy Electron ) from the Nucleus of an Atom. Beta Decay does not change the Mass Number, but increases the Atomic Number by 1.

Radioactive Emission of a Beta Particle ( consisting of a High Energy Electron ) from the Nucleus of an Atom. Beta Decay does not change the Mass Number, but increases the Atomic Number by 1.

### Gamma Decay

Gamma Decay

### Radioactive Emission of a Gamma Ray from the Nucleus of an Atom. Gamma decay does not change either the Mass Number or the Atomic Number.

Radioactive Emission of a Gamma Ray from the Nucleus of an Atom. Gamma decay does not change either the Mass Number or the Atomic Number.

### Nuclear Fission

Nuclear Fission

### A Large Atomic Nucleus is Split into two ( or more ) smaller Nuclei, releasing several Neutrons and Energy.

A Large Atomic Nucleus is Split into two ( or more ) smaller Nuclei, releasing several Neutrons and Energy.

### Nuclear Fusion

Nuclear Fusion

### Two small Nuclei combine under high temperatures and pressures to form a larger Nucleus, releasing Energy.

Two small Nuclei combine under high temperatures and pressures to form a larger Nucleus, releasing Energy.

### Simple Harmonic Motion

Simple Harmonic Motion

### The motion of an Object oscillating around a fixed equilibrium position. The acceleration of the Object is proportional to its displacement, and is always directed towards the equilibrium point.

The motion of an Object oscillating around a fixed equilibrium position. The acceleration of the Object is proportional to its displacement, and is always directed towards the equilibrium point.

### Travelling Wave

Travelling Wave

### A Wave in which Energy is transferred from one point to another by vibrations.

A Wave in which Energy is transferred from one point to another by vibrations.

### Stationary Wave

Stationary Wave

### A Wave in which the points of zero and maximum displacement do not move through the medium.

A Wave in which the points of zero and maximum displacement do not move through the medium.

### Node

Node

### A point on a Standing wave where there is zero displacement. Occurs due to destructive interference between the incident and reflected wave.

A point on a Standing wave where there is zero displacement. Occurs due to destructive interference between the incident and reflected wave.

### Damping

Damping

### A decrease in the amplitude of oscillations due to the loss of energy from the oscillating system, for example the loss of energy due to work against friction.

A decrease in the amplitude of oscillations due to the loss of energy from the oscillating system, for example the loss of energy due to work against friction.

### Wavelength

Wavelength

### The distance between any two repeating points within a Wave, measured in Meters.

The distance between any two repeating points within a Wave, measured in Meters.

### Amplitude

Amplitude

### The vertical distance between the peak ( or trough ) of a wave and the Equilibrium Point.

The vertical distance between the peak ( or trough ) of a wave and the Equilibrium Point.

### Period

Period

### The Time Taken for One wave to Pass a point, measured in Seconds.

The Time Taken for One wave to Pass a point, measured in Seconds.

### Frequency

Frequency

### The Number of Waves passing a point in One Second, measured in Hertz.

The Number of Waves passing a point in One Second, measured in Hertz.

### Coherent Wave

Coherent Wave

### Coherent Waves have Same frequency, wavelength and speed and are in phase.

Coherent Waves have Same frequency, wavelength and speed and are in phase.

### Constructive Interference

Constructive Interference

### When 2 wave crests or 2 wave troughs arrive at the same point at the same time, they are said to be in phase, causing a Maximum. The superposition of these two waves results in a stronger signal.

When 2 wave crests or 2 wave troughs arrive at the same point at the same time, they are said to be in phase, causing a Maximum. The superposition of these two waves results in a stronger signal.

### Destructive Interference

Destructive Interference

### When a wave crest and a wave trough arrive at the same point at the same time, they are said to be out of phase, causing a Minimum. The superposition of these two waves causes the signals to be cancel each other out.

When a wave crest and a wave trough arrive at the same point at the same time, they are said to be out of phase, causing a Minimum. The superposition of these two waves causes the signals to be cancel each other out.

### Optical Path Difference

Optical Path Difference

### The Optical Path is equal to the product of the Physical Path Difference and the Refractive Index. Used when two rays pass through materials with different Refractive Indices before interfering.

The Optical Path is equal to the product of the Physical Path Difference and the Refractive Index. Used when two rays pass through materials with different Refractive Indices before interfering.

### LASER

LASER

### Light Amplification by Stimulated Emission of Radiation, gives Monochromatic and coherent light

Light Amplification by Stimulated Emission of Radiation, gives Monochromatic and coherent light

### Point Source

Point Source

### A source which emits Electromagnetic Radiation equally in all directions.

A source which emits Electromagnetic Radiation equally in all directions.

### Irradiance

Irradiance

### The amount of Light Energy incident on every square metre of a surface per second.

The amount of Light Energy incident on every square metre of a surface per second.

### Work Function

Work Function

### The minimum energy which must be supplied to by each Photon enable an electron to escape from a metal surface.

The minimum energy which must be supplied to by each Photon enable an electron to escape from a metal surface.

### Threshold Frequency

Threshold Frequency

### The Minimum Frequency of a Photon required to cause an Electron to undergo Photoelectric Emission.

The Minimum Frequency of a Photon required to cause an Electron to undergo Photoelectric Emission.

### Spontaneous Emission

Spontaneous Emission

### Light is emitted when electrons in an excited state drop to a lower energy level. Emitting photons in any direction, randomly.

Light is emitted when electrons in an excited state drop to a lower energy level. Emitting photons in any direction, randomly.

### Stimulated Emission

Stimulated Emission

### An incoming photon causes an electron to jump down to a lower energy level and emit a photon. The photons are in phase and moving parallel to each other in the same direction.

An incoming photon causes an electron to jump down to a lower energy level and emit a photon. The photons are in phase and moving parallel to each other in the same direction.

### Stimulated Absorption

Stimulated Absorption

### Incoming photons are absorbed by electrons in a lower energy level causing them to jump to a higher energy level.

Incoming photons are absorbed by electrons in a lower energy level causing them to jump to a higher energy level.

### Unpolarised Light

Unpolarised Light

### Light in which the Electric Field oscillations occur in random Planes.

Light in which the Electric Field oscillations occur in random Planes.

### Optical Activity

Optical Activity

### The effect of some materials of rotating the Plane of Polarisation of a Beam of Light passing through it.

The effect of some materials of rotating the Plane of Polarisation of a Beam of Light passing through it.

### Polarised Light

Polarised Light

### Light in which all Electric Field oscillations are in one Plane.

Light in which all Electric Field oscillations are in one Plane.

### Saccharimetry

Saccharimetry

### Technique that uses the Optical Activity of a Sugar solution to measure its concentration.

Technique that uses the Optical Activity of a Sugar solution to measure its concentration.

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## Miscellaneous

Miscellaneous

### Mains supply frequency - 50Hz

Mains supply frequency - 50Hz

### Mains supply voltage - 230V

Mains supply voltage - 230V

### Evidence for particle theory - Photoelectric effect

Evidence for particle theory - Photoelectric effect

### Evidence for wave theory/ test for wave - Interference Patterns

Evidence for wave theory/ test for wave - Interference Patterns

### Dispersion using a prism - Red deviates least, Violet deviates most

Dispersion using a prism - Red deviates least, Violet deviates most

### Interference diffraction grating - Red deviates most, Violet deviates least

Interference diffraction grating - Red deviates most, Violet deviates least