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Specific charge
the charge to mass ratio or charge in coulombs divided by the mass in kilograms
Isotope
a nucleus with the same number of protons but different number of neutrons
Hadron
a particle that experiences the strong nuclear force. Composite particles made of either qqq (baryons) or q anti-q (baryon)
Antimatter
Particles with the same mass but opposite charge
Photoelectric effect
the emission of electrons from metal surfaces by light of an appropriate frequency
Photon
a discrete packet/quantum of electromagnetic energy
Work function
the minimum energy required for an electron to escape from the surface of the metal
Threshold frequency
the minimum frequency of a photon required to release electrons from the surface of a metal
Electron volt
the energy given to an electron when it passes through a potential difference of 1 V
Energy Level
Allowed/discrete energy of an atom or electron in an atom
Ionisation energy of an atom
the minimum energy required to remove an electron from an atom in its ground state
Excitation energy
the energy required to move an electron from a lower energy level to a higher energy level
Line spectra
the characteristic wavelengths of light produced by individual excited atoms
Longitudinal waves
direction of oscillation is parallel to the direction of wave travel. Wave travels with series compressions and rarefactions.
Transverse waves
direction of oscillation is perpendicular to the direction of wave travel with peaks and troughs.
Electromagnetic wave
a transverse wave, consisting of a changing magnetic field at right angles to a changing electric field
Amplitude
the maximum displacement from the equilibrium position
Frequency
the number of oscillations per second
Wavelength
the shortest distance between two consecutive particles in a wave which are in phase
Wave speed
the speed of energy transfer through the medium
Diffraction
Diffraction is the spreading out of a wave as it passes through an aperture/around an obstacle.
Polarised waves
electromagnetic waves where the oscillations are in one direction only that is 90° to the direction of wave travel
Unpolarised waves
electromagnetic waves where the oscillations are in many directions
Refractive index
the absolute refractive index of the substance is the speed of light in a vacuum divided by the speed of light in the substance, n = Vc/Vs
Critical angle
the angle of incidence on a boundary between two media when the angle of refraction is 90°
Total internal reflection
total internal reflection occurs when an EM wave goes from a more dense to less dense medium and the angle of incidence is greater than critical angle. All the light is reflected within the substance
Step index fibre
there is a sudden change in refractive index between the core and the cladding
Path difference
the difference in distance one wave has to travel to reach a point compared to another wave
Superposition
when two or more waves of the same type meet at a point the resultant displacement of will be the sum of the individual displacements
Stationary wave
a stationary wave is formed by two waves of the same frequency and similar amplitude travelling in opposite directions. There is no net energy transfer.
Node
a point on stationary wave with zero amplitude
Antinode
a point on stationary wave with maximum amplitude
Fundamental frequency
the lowest frequency of a wave which will produce a stationary wave
Coherence
coherent waves have a constant phase relationship and the same frequency
Monochromatic
waves of only one frequency
Fringe spacing
the distance between two consecutive maxima or minima in an interference pattern
Electric current
the number of coulombs of charge passing a point per second (I=Q/t)
Potential difference
the work done per unit charge when charges move from one point in the circuit to another (V=E/Q)
Resistance
the ratio of the potential difference across a component to the current through it
Ohmic conductor or resistor
the ratio of potential difference to current remains constant. Resistance is constant. It follows Ohm's Law (R=V/I)
Ohm's law
the current through component is proportional to the potential difference across it (R=V/I)
Superconductivity
A material that has zero resistivity below a certain temperature (the critical temperature, Tc)
Critical temperature, Tc
the temperature at or below which the resistivity of a superconductor becomes zero
Kirchhoff's first law
the sum of the currents into the junction is zero. The current in any one series loop is constant
Kirchhoff's second law
in any closed loop the sum of the supply voltage equals the sum of the potential differences
EMF, ε
energy provided (transferred from chemical to electrical) by the cell per unit charge
Internal resistance, r
the resistance inside a battery, cell or power supply
Lost volts
the voltage drop across the internal resistance of the power supply.
Terminal PD, V
energy per unit charge available to be transferred into other forms by the circuit. It can be found by measuring the voltage across a cell when the current is zero
Scalar
a quantity which has magnitude only
Vector
a quantity which has magnitude and direction
Equilibrium
an object is in equilibrium when the resultant force on it is zero and the resultant moment is zero
Moment/torque
the moment/torque/turning force about point is the force multiplied by the perpendicular distance from the point to the line of action of the force
Principle of moments
for an object in equilibrium the sum of the clockwise moments equals the sum of the anticlockwise moments
Couple
two equal and opposite forces separated by a distance D between the lines of action of the forces (this produces rotational motion only)
Centre of mass
the point at which the whole mass of the object appears to act
Displacement
the distance an object has moved in a particular direction
Speed
rate of change of distance
Velocity
rate of change of displacement
Acceleration
the rate of change of velocity
Parabolic path
the shape of the path of a particle moving with a component of motion at right angles to a constant resultant force (constant acceleration)
Newton's first law
an object remains at rest or moves with a constant velocity providing no resultant external force is applied
Newton's second law
for a constant mass the acceleration of the object is proportional to the resultant force applied to it
Newton's third law
all forces occur in pairs of same size and type but opposite direction and on opposite objects
Work
work done equals force multiplied by the distance moved in the direction of the force
Power
power equals work done per unit time
Principle of conservation of energy
energy cannot be created or destroyed it can only be changed from one form to another
Elastic Collision
an interaction where kinetic energy is conserved
Inelastic Collision
an interaction where kinetic energy is not conserved
Density
the mass per unit volume
Hooke's law
the extension of a spring or material is proportional to the tensile force applied (this applies up to the limit of proportionality of the material). The line must start at the origin and be straight
Elastic behaviour
will return to its original shape after deforming forces are removed
Plastic behaviour
will not return to its original shape after deforming forces are removed
Brittle
a brittle material will not undergo plastic deformation before fracture. It does not absorb lots of energy before fracture.
stress, σ
tensile force per unit cross-sectional area of the material
strain, ε
extension per unit length
Young's modulus, E
stress divided by strain
Fracture
this is when the material breaks. Materials are compared by their ultimate tensile stress, this is the tensile stress needed to break the material (strength of material)
Potential Divider
A combination of resistors in series that splits voltage
Tensile Deformation
Changing the shape of a sample by an increase in extension (stretching)
Compressive Deformation
Changing the shape of a sample by a decrease in extension (squashing)
Note
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