Upper secondaryCode 9702
Physics
76 topics and 300 objectives, each one something you should be able to do.
Written by Kindred in its own plain words. Your syllabus is still the official list, so check it for anything exact.
What this subject asks you to be able to do
1.1Physical quantities2 objectives
- understand that any physical quantity comprises a numerical magnitude together with a unit
- make sensible estimates of the physical quantities met in this course
1.2SI units4 objectives
- recall each of these SI base quantities and its unit: mass (kg), length (m), time (s), current (A), temperature (K)
- express a derived unit as a product or quotient of SI base units, and use derived units where appropriate for the quantities covered in this course
- apply SI base units to verify that physical equations are homogeneous
- recall the prefixes pico (p), nano (n), micro (μ), milli (m), centi (c), deci (d), kilo (k), mega (M), giga (G) and tera (T), with their symbols, and use them to show decimal multiples or submultiples of base units and of derived units
1.3Errors and uncertainties3 objectives
- understand and explain how random errors and systematic errors (including zero errors) affect measurements
- understand how precision differs from accuracy
- assess the uncertainty carried by a derived quantity when absolute or percentage uncertainties are simply added together
1.4Scalars and vectors3 objectives
- understand how scalar and vector quantities differ, and give examples of each from this course
- carry out addition and subtraction on coplanar vectors
- represent any vector by a pair of perpendicular components
2.1Equations of motion9 objectives
- define distance, displacement, speed, velocity and acceleration, and use them
- use graphs as a way of representing each of distance, displacement, speed, velocity and acceleration
- work out displacement by finding the area beneath a velocity–time graph
- find velocity from a displacement–time graph by measuring its gradient
- find acceleration from a velocity–time graph by measuring its gradient
- derive, starting from how velocity and acceleration are defined, the equations for straight-line motion with uniform acceleration
- solve problems with the equations for straight-line motion at uniform acceleration, including bodies falling without air resistance in a uniform gravitational field
- describe an experiment in which a falling object is used to find the acceleration of free fall
- describe and explain the motion of an object that has uniform velocity in one direction and, at the same time, uniform acceleration in the perpendicular direction
3.1Momentum and Newton’s laws of motion6 objectives
- understand that an object's mass is the quantity giving it resistance to a change in its movement
- recall F = ma and use it to solve problems, knowing that the acceleration always points the same way as the resultant force
- define linear momentum as the result of multiplying mass by velocity, and use it
- define force as the rate at which momentum changes, and use it
- state Newton’s laws of motion, one by one, and apply each of them
- describe and use the idea of weight as the force a gravitational field exerts on a mass, and also recall that an object's weight equals its mass multiplied by the acceleration of free fall
3.2Non-uniform motion3 objectives
- show a qualitative understanding of friction and of viscous or drag forces, including air resistance (no work with the coefficients of friction or viscosity is needed, and a simple model in which drag rises with speed is enough)
- describe, and account for in qualitative terms, how objects move within a uniform gravitational field when air resistance acts on them
- understand that a terminal (constant) velocity may be attained by objects travelling against a resistive force
3.3Linear momentum and its conservation4 objectives
- state the principle that momentum is conserved
- apply momentum conservation to simple questions, including elastic and inelastic interactions involving bodies in one and two dimensions (the coefficient of restitution concept is not required)
- recall that, in an elastic collision, overall kinetic energy remains unchanged and the speed at which the objects approach each other equals the speed at which they move apart
- understand that in any interaction between objects the momentum of the system is always conserved, though its kinetic energy may change
4.1Turning effects of forces4 objectives
- understand that an object's weight can be treated as acting at one point, called its centre of gravity
- define the moment of a force and apply that idea
- understand that a couple, made of two forces, causes rotation only
- define the torque of a couple, and put it to use
4.2Equilibrium of forces3 objectives
- give a statement of the principle of moments, then apply it
- appreciate that a system is in equilibrium if there is no resultant force, and likewise no resultant torque, acting on it
- apply vector triangles to represent coplanar forces that are in equilibrium
4.3Density and pressure6 objectives
- define and use density
- define and use pressure
- derive, starting from how pressure and density are defined, the equation ∆p = ρg∆h for the hydrostatic pressure difference
- apply the hydrostatic pressure equation ∆p = ρg∆h
- understand that a difference in hydrostatic pressure is what produces the upthrust on a body in a fluid
- work out the upthrust on a body in a fluid by means of F = ρgV (Archimedes’ principle)
5.1Energy conservation7 objectives
- understand the idea of work, and state and apply the expression work done = force × displacement, with the displacement measured along the line in which the force acts
- recall the principle that energy is conserved, and apply it
- recall and understand that a system's efficiency is the ratio of the useful energy it gives out to the total energy put into it
- apply the idea of efficiency when working through problems
- define power as the amount of work completed in each unit of time
- solve questions by means of P = W/t
- derive P = Fv and employ it when working through problems
5.2Gravitational potential energy and kinetic energy4 objectives
- derive, from W = Fs, the expression ∆EP = mg∆h giving gravitational potential energy changes within a uniform gravitational field
- recall ∆EP = mg∆h and use it to find changes in gravitational potential energy in a uniform gravitational field
- derive the expression for kinetic energy, EK = 1/2 mv², by working from the equations of motion
- recall and apply EK = 1/2 mv²
6.1Stress and strain6 objectives
- appreciate that tensile or compressive forces bring about deformation (forces and deformations are taken to act in one dimension only)
- appreciate and apply the vocabulary of load, extension, compression and limit of proportionality
- recall and apply Hooke’s law
- recall the spring constant formula k = F/ x and use it
- define stress, strain and the Young modulus, and make use of these terms
- describe how to find the Young modulus of a metal by an experiment on a length of wire
6.2Elastic and plastic behaviour4 objectives
- understand the meaning of, and be able to apply, the terms elastic deformation, plastic deformation and elastic limit
- understand that the work done is given by the area beneath the force–extension graph
- find the elastic potential energy stored in a material whose deformation stays within its limit of proportionality, using the area under its force–extension graph
- recall EP = 1/2 Fx = 1/2 kx² and use it for a material's deformation up to its limit of proportionality
7.1Progressive waves7 objectives
- describe the idea of wave motion, shown through vibrations in ropes, springs and ripple tanks
- understand what displacement, amplitude, phase difference, period, frequency, wavelength and speed mean, and use these terms
- understand how a cathode-ray oscilloscope (CRO) uses its time-base and y-gain settings to find frequency and amplitude
- derive the wave equation v = f λ by starting from the definitions of speed, frequency and wavelength
- recall and apply the relation v = f λ
- understand that a progressive wave carries energy from one place to another
- recall that, for a progressive wave, intensity = power/area and also intensity ∝ (amplitude)², and use both relations
7.2Transverse and longitudinal waves2 objectives
- compare the features of transverse waves with those of longitudinal waves
- analyse and make sense of graphs that depict transverse and longitudinal waves
7.3Doppler effect for sound waves2 objectives
- understand that if a sound source moves relative to an observer at rest, the frequency the observer detects differs from the frequency the source gives out (the Doppler effect when the observer moves and the source stays still is not required)
- apply the expression fο = f s v/(v ± vs) to work out the observed frequency when a sound wave source is moving with respect to a stationary observer
7.4Electromagnetic spectrum3 objectives
- give the statement that every electromagnetic wave is a transverse wave which moves at the same speed c through free space
- recall roughly how long the wavelengths in free space are for each main region of the electromagnetic spectrum, running from radio waves through to γ-rays
- recall that wavelengths of 400–700nm in free space are picked up by the human eye as visible light
7.5Polarisation2 objectives
- understand that transverse waves are linked with the phenomenon of polarisation
- recall Malus’s law (I = I0 cos²θ) and use it to calculate the intensity of plane-polarised electromagnetic waves after they pass through one polarising filter or several in a row (calculating how a polarising filter changes the intensity of unpolarised waves is not required)
8.1Stationary waves4 objectives
- account for and apply the superposition principle
- show an understanding of experiments in which air columns, stretched strings and microwaves produce stationary waves (end corrections are taken as negligible, and the concept of end correction does not need to be known)
- account for how a stationary wave forms by means of a graphical approach, and pick out nodes and antinodes
- understand how the wavelength can be found from where the nodes or antinodes of a stationary wave sit
8.2Diffraction2 objectives
- explain what is meant by the term diffraction
- show an understanding of experiments in which diffraction is seen, including, in qualitative terms, how the gap width compared with the wavelength affects it; for example, water waves diffracting in a ripple tank
8.3Interference4 objectives
- appreciate what is meant by the words interference and coherence
- show that you grasp the investigations that reveal two-source interference in water waves in a ripple tank, and in sound, light and microwaves
- know which conditions must hold for two-source interference fringes to be seen
- recall λ = ax /D and apply it to double-slit interference with light
8.4The diffraction grating2 objectives
- recall and apply the relationship d sin θ = nλ
- describe how a diffraction grating is used to find the wavelength of light (how a spectrometer is built and used is not included)
9.1Electric current4 objectives
- understand that flowing charge carriers make up an electric current
- understand that the amount of charge a charge carrier holds is quantised
- recall and apply the relationship Q = It
- apply the expression I = Anvq to a current-carrying conductor, where n stands for the number density of charge carriers
9.2Potential difference and power3 objectives
- define potential difference as the energy transferred for each unit of charge across a component
- recall and apply V = W/Q
- recall and apply P = VI, P = I²R and P = V²/R
9.3Resistance and resistivity8 objectives
- define resistance
- recall and apply V = IR
- sketch the I–V characteristic for each of: a filament lamp, a semiconductor diode, and a metal conductor whose temperature stays constant
- account for a filament lamp's resistance going up as the current rises, since its temperature also goes up
- state Ohm’s law
- recall and apply R = ρL/A
- understand that a light-dependent resistor (LDR) has a resistance that falls as light intensity rises
- understand that a thermistor's resistance drops as its temperature rises (it is assumed that thermistors possess a negative temperature coefficient)
10.1Practical circuits5 objectives
- recall and use the circuit symbols that section 6 sets out
- draw and interpret circuit diagrams built from the circuit symbols that section 6 sets out
- define the electromotive force (e.m.f.) of a source as the energy it transfers per unit charge when it drives charge round a complete circuit, and use this definition
- distinguish between e.m.f. and potential difference (p.d.) by looking at them from the standpoint of energy
- understand how the internal resistance of an e.m.f. source affects the terminal potential difference
10.2Kirchhoff’s laws7 objectives
- state Kirchhoff’s first law and grasp that it stems from the conservation of charge
- state Kirchhoff’s second law and understand that it comes from energy being conserved
- derive, from Kirchhoff’s laws, an expression for the combined resistance when two or more resistors are joined in series
- use the formula that gives the combined resistance of a series arrangement of two or more resistors
- derive, from Kirchhoff’s laws, an expression for the combined resistance when two or more resistors are joined in parallel
- use the formula that gives the combined resistance when two or more resistors are placed side by side in parallel
- apply Kirchhoff’s laws to tackle straightforward circuit problems
10.3Potential dividers4 objectives
- understand the underlying idea behind a potential divider circuit
- recall and use the principle by which a potentiometer compares potential differences
- understand how null methods rely on a galvanometer
- explain how thermistors and light-dependent resistors are used in potential dividers so that the potential difference depends on temperature and light intensity
11.1Atoms, nuclei and radiation12 objectives
- infer, using the outcomes of the α-particle scattering experiment, that the nucleus is present and of small size
- describe a basic model of the nuclear atom, with protons, neutrons and orbital electrons as its parts
- distinguish proton number from nucleon number
- understand that isotopes are variants of a single element that differ in how many neutrons their nuclei contain
- understand and apply the A/Z X notation when representing nuclides
- understand that every nuclear process conserves both nucleon number and charge
- outline the mass, charge and composition of α-, β- and γ-radiations, with both β– (electrons) and β+ (positrons) included
- understand that the antiparticle of a given particle matches it in mass yet carries the reverse charge, and that the antiparticle of an electron is the positron
- state that in β– decay an (electron) antineutrino is produced, and in β+ decay an (electron) neutrino
- understand that α-particles have discrete energies, whereas the energies of β-particles cover a continuous range, since β-decay also emits (anti)neutrinos
- represent α- and β-decay by writing radioactive decay equations like UTh 92 238 90 234 2 " + 4α
- use the unified atomic mass unit (u) to express masses
11.2Fundamental particles6 objectives
- understand that quarks are fundamental particles, and that six kinds of quark, known as flavours (types), are present: up, down, strange, charm, top and bottom
- recall and use the charge carried by each quark flavour, and understand that the matching antiquark has the opposite charge (no other properties of quarks need to be known)
- recall that the proton and the neutron are not fundamental particles, and describe the quark composition of each
- understand that hadrons are of two kinds: baryons, made up of three quarks, and mesons, made up of a quark and an antiquark
- describe what happens to the quark composition during β– and β+ decay
- recall that the name lepton is given to electrons and neutrinos, which are fundamental particles
12.1Kinematics of uniform circular motion3 objectives
- define a radian, then represent an angular displacement with radians
- understand what angular speed is and use it
- recall the relations ω = 2π/T and v = rω and apply them
12.2Centripetal acceleration4 objectives
- understand that centripetal acceleration is produced by a force of unchanging magnitude that is always at right angles to the direction of motion
- understand that centripetal acceleration is what brings about circular motion at a steady angular speed
- recall and apply the relationships a = rω² and a = v²/r
- recall and apply the expressions F = mrω² and F = mv²/r
13.1Gravitational field2 objectives
- understand that a gravitational field is one kind of field of force, and define it as the force on each unit of mass
- represent a gravitational field with the aid of field lines
13.2Gravitational force between point masses4 objectives
- appreciate that a uniform sphere's mass can be treated as a point mass located at its centre, when the point under consideration lies outside the sphere
- recall Newton’s law of gravitation, F = Gm1m2 /r², and apply it to the force acting between two point masses
- analyse circular orbits in a gravitational field by treating the gravitational force as the cause of the centripetal acceleration
- understand that a geostationary satellite keeps the same position above the Earth’s surface: it orbits once every 24 hours, travelling west to east directly over the Equator
13.3Gravitational field of a point mass3 objectives
- derive the equation g = GM/r² for a point mass's gravitational field strength, starting from Newton’s law of gravitation together with the definition of gravitational field
- recall and apply g = GM/r²
- understand why g can be taken as constant over small height changes close to the Earth’s surface
13.4Gravitational potential3 objectives
- define gravitational potential at a location as the amount of work performed for each unit of mass when a small test mass is moved from infinity to that location
- apply ϕ = –GM/r to obtain the gravitational potential within the field created by a point mass
- understand how gravitational potential energy for a pair of point masses follows from the idea of gravitational potential, and use EP = –GMm/r
14.1Thermal equilibrium2 objectives
- understand that (thermal) energy flows from a hotter region to a cooler one
- understand that when regions have equal temperatures, they are in thermal equilibrium
14.2Temperature scales4 objectives
- understand that any physical property that changes with temperature can be used to measure temperature, and give examples, including a liquid's density, the volume of a gas held at constant pressure, a metal's resistance and the e.m.f. of a thermocouple
- appreciate that the thermodynamic temperature scale does not rely on the characteristics of any single substance
- convert temperature values in either direction, kelvin to degrees Celsius and the reverse, and recall that T/K = θ/°C + 273.15
- understand that absolute zero is the name for zero kelvin, the lowest temperature possible on the thermodynamic temperature scale
14.3Specific heat capacity and specific latent heat2 objectives
- define specific heat capacity and apply it
- define specific latent heat, apply it, and distinguish the specific latent heat of fusion from that of vaporisation
15.1The mole2 objectives
- understand that amount of substance belongs among the SI base quantities, with mol as its base unit
- use molar quantities, taking a mole of any substance as the amount of it that holds the same number of particles as the Avogadro constant NA
15.2Equation of state3 objectives
- appreciate that a gas for which pV ∝ T, with T the thermodynamic temperature, is called an ideal gas
- recall and use the ideal gas equation of state in two forms: pV = nRT, with n = the amount of substance in moles, and pV = NkT, with N = the number of molecules
- recall that k, the Boltzmann constant, is expressed as k = R/NA
15.3Kinetic theory of gases4 objectives
- give the fundamental assumptions on which the kinetic theory of gases rests
- explain how the movement of molecules gives rise to gas pressure, and derive and use pV = 1/3 Nm<c²>, where <c²> is the mean-square speed (a simple model of one-dimensional collisions, extended to three dimensions using 1/3 <c²> = <cx²>, is enough)
- understand that cr.m.s., the root-mean-square speed, is equal to <c²>
- compare pV = 1/3 Nm<c²> with pV = NkT and conclude that a molecule's average translational kinetic energy comes to 2/3 kT, then recall and apply this expression
16.1Internal energy2 objectives
- understand that the state of a system determines its internal energy, which equals the sum of the randomly distributed kinetic and potential energies of its molecules
- relate a rise in an object's temperature to a growth in its internal energy
16.2The first law of thermodynamics2 objectives
- recall W = p∆V for the work done when a gas expands or is compressed at constant pressure, and use it; understand how work done by the gas differs from work done on it
- recall the first law of thermodynamics, ∆U = q + W, and use it, where ∆U is the rise in internal energy, q is the heating of the system (the energy it gains by heating) and W is the work done on it
17.1Simple harmonic oscillations5 objectives
- understand and apply the vocabulary of displacement, amplitude, period, frequency, angular frequency and phase difference as it applies to oscillations, and express the period through frequency and also through angular frequency
- understand that simple harmonic motion arises if the acceleration is in direct proportion to the displacement from a fixed point and is directed oppositely to it
- use a = –ω²x; recall x = x0 sin ωt, one solution of that equation, and use it
- apply the two velocity equations v = v0 cos ωt and v = ±ω√(x0² − x²)
- analyse and interpret graphical representations showing how displacement, velocity and acceleration change in simple harmonic motion
17.2Energy in simple harmonic motion2 objectives
- outline how energy passes back and forth between kinetic and potential forms as a body performs simple harmonic motion
- recall and use E = 1/2 mω²x0², which gives the total energy possessed by a system in simple harmonic motion
17.3Damped and forced oscillations, resonance3 objectives
- understand that damping is produced whenever a resisting force is applied to a system in oscillation
- understand and apply the labels light, critical and heavy damping, and sketch displacement–time graphs that illustrate each of these damping types
- understand that resonance means the amplitude of oscillations reaches a maximum, which happens when an oscillating system is driven to vibrate at its natural frequency
18.1Electric fields and field lines3 objectives
- understand that an electric field is one kind of field of force, and define it as the force on each unit of positive charge
- recall F = qE, the force a charge experiences in an electric field, and use it
- represent an electric field with the aid of field lines
18.2Uniform electric fields2 objectives
- recall and use E = ∆V/∆d to work out how strong the uniform field is between a pair of charged parallel plates
- describe how a uniform electric field alters the movement of charged particles
18.3Electric force between point charges2 objectives
- understand that the charge on a spherical conductor can be treated as a point charge located at its centre when the point in question lies outside the sphere
- recall and apply Coulomb's law, F = Q1Q2/(4πε0r²), to work out the electrostatic force acting between a pair of point charges in free space
18.4Electric field of a point charge1 objective
- recall and apply E = Q/(4πε0r²) to find the electric field strength produced by a point charge in free space
18.5Electric potential4 objectives
- define the electric potential at a location as the amount of work needed per unit of positive charge to move a small test charge from an infinite distance to that location
- recall and apply the result that the electric field at a given point equals minus the potential gradient at that same point
- apply V = Q/(4πε0r) when finding the electric potential of the field produced by a point charge
- understand how electric potential gives rise to the electric potential energy possessed by a pair of point charges, and apply EP = Qq/(4πε0r)
19.1Capacitors and capacitance4 objectives
- define capacitance, with reference to isolated spherical conductors and parallel plate capacitors alike
- recall and apply the relationship C = Q/V
- derive, starting from C = Q/V, the expressions giving total capacitance for capacitors wired in series and in parallel
- apply the expressions for total capacitance when capacitors are connected in series and when they are connected in parallel
19.2Energy stored in a capacitor2 objectives
- find the electric potential energy a capacitor stores, using the area under its potential–charge graph
- state and apply W = 1/2 QV = 1/2 CV²
19.3Discharging a capacitor3 objectives
- analyse graphs showing how the potential difference, charge and current of a capacitor change over time as it discharges through a resistor
- recall and use τ = RC as the time constant when a capacitor discharges via a resistor
- use equations like x = x0 e–(t/RC) for a capacitor that discharges through a resistor, where x can stand for the current, the charge or the potential difference
20.1Concept of a magnetic field2 objectives
- understand that moving charges and permanent magnets each produce a magnetic field, which is one kind of field of force
- represent any magnetic field as a pattern of field lines
20.2Force on a current-carrying conductor3 objectives
- know that a current-carrying conductor placed in a magnetic field may experience a force
- recall and apply the equation F = BIL sin θ, with the directions read off using Fleming's left-hand rule
- define the magnetic flux density of a field as the force on a wire lying at right angles to that field, per unit length of wire and per unit current
20.3Force on a moving charge6 objectives
- work out which way a force acts on a charge travelling through a magnetic field
- state and apply F = BQv sin θ
- understand how the Hall voltage arises, then derive VH = BI/(ntq), with t = thickness, and use it
- understand how a Hall probe is employed to measure magnetic flux density
- describe how a charged particle behaves when it travels through a uniform magnetic field, with the field perpendicular to the particle's direction of travel
- account for the way electric and magnetic fields may be put to use in velocity selection
20.4Magnetic fields due to currents3 objectives
- sketch the magnetic field pattern produced by the current in each of these: a long solenoid, a long straight wire and a flat circular coil
- appreciate that a ferrous core strengthens the magnetic field produced by the current in a solenoid
- account for the origin of the forces acting between current-carrying conductors and work out which way those forces point
20.5Electromagnetic induction5 objectives
- define magnetic flux as the outcome of multiplying magnetic flux density by the area of cross-section taken perpendicular to the direction in which the flux density points
- recall and apply Φ = BA
- understand the idea of magnetic flux linkage and apply it
- understand and explain experiments which show: that an e.m.f. can be induced in a circuit by a changing magnetic flux; that the induced e.m.f. acts in a direction that opposes the change causing it; and which factors affect the magnitude of the induced e.m.f.
- recall Faraday’s and Lenz’s laws of electromagnetic induction and put them into practice
21.1Characteristics of alternating currents4 objectives
- understand what period, frequency and peak value mean for an alternating current or voltage, and use these terms
- use equations of the type x = x0 sin ωt to describe an alternating current or voltage that varies sinusoidally
- recall and use the idea that a resistive load's mean power, when the alternating current is sinusoidal, is half of its maximum power
- distinguish root-mean-square (r.m.s.) values from peak values, and also recall and apply I r.m.s. = I0 / 2 and Vr.m.s. = V0 / 2 when the alternating current is sinusoidal
21.2Rectification and smoothing4 objectives
- distinguish half-wave rectification from full-wave rectification by means of graphs
- explain how a single diode is employed to half-wave rectify an alternating current
- explain how four diodes arranged as a bridge rectifier are used to full-wave rectify an alternating current
- analyse what a single capacitor does when used for smoothing, including how the values of capacitance and load resistance change its effect
22.1Energy and momentum of a photon5 objectives
- understand that electromagnetic radiation is particulate in nature
- understand that one quantum of electromagnetic energy is called a photon
- recall and apply the relation E = hf
- use the electronvolt (eV) for measuring energy
- appreciate that a photon carries momentum, which equals p = E/c
22.2Photoelectric effect5 objectives
- understand that a metal surface can release photoelectrons when electromagnetic radiation falls on it
- understand what the threshold frequency and the threshold wavelength are, and use both terms
- account for photoelectric emission by reference to photon energy and work function energy
- state and apply hf = Φ + 1/2 mvmax²
- account for why the maximum kinetic energy of photoelectrons does not depend on intensity, in contrast to the photoelectric current, which is proportional to intensity
22.3Wave-particle duality4 objectives
- understand that the photoelectric effect is evidence that electromagnetic radiation has a particulate nature, whereas phenomena such as interference and diffraction are evidence that it has a wave nature
- outline and interpret, qualitatively, the evidence that electron diffraction gives for particles having a wave nature
- appreciate what the de Broglie wavelength means: the wavelength linked to a particle that is in motion
- state and apply λ = h/p
22.4Energy levels in atoms and line spectra3 objectives
- appreciate that isolated atoms, e.g. atomic hydrogen, have electrons confined to energy levels that are discrete
- understand what emission and absorption line spectra look like and how they come about
- state hf = E1 – E2 and apply it
23.1Mass defect and nuclear binding energy7 objectives
- understand that E = mc² expresses the equivalence of mass and energy, and recall and use this equation
- represent basic nuclear reactions using nuclear equations in the layout 7NHeO H 14 2 4 8 17 1 1 ++
- define mass defect and binding energy, and make use of both terms
- sketch how binding energy per nucleon varies against nucleon number
- explain the definitions of nuclear fusion and nuclear fission
- account for why binding energy per nucleon matters in nuclear reactions, including nuclear fusion and nuclear fission
- work out the energy given off in nuclear reactions from E = c²∆m
23.2Radioactive decay6 objectives
- understand that the count rate's fluctuations give evidence for radioactive decay being random in nature
- know that radioactive decay happens both spontaneously and at random
- define activity and decay constant, and state the relationship A = λN and apply it
- define half-life
- use λ = 0.693/t₁/₂
- understand that radioactive decay is exponential in character, and sketch and apply x = x₀e–λt, where x may stand for activity, the number of undecayed nuclei or the received count rate
24.1Production and use of ultrasound6 objectives
- understand that applying a p.d. across a piezo-electric crystal makes it change shape, and that changing its shape makes the crystal generate an e.m.f.
- understand how a piezoelectric transducer creates ultrasound waves and detects them
- understand how ultrasound pulses reflected at the boundaries between tissues can give diagnostic information about internal structures
- define a medium's specific acoustic impedance as Z = ρc, in which c stands for the speed of sound within that medium
- use IR / I0 = (Z₁ – Z₂)² / (Z₁ + Z₂)² in order to get the intensity reflection coefficient across a boundary joining two media
- recall I = I₀e–μx and use it to work out how ultrasound is attenuated as it passes through matter
24.2Production and use of X-rays4 objectives
- explain that X-rays are produced when electrons bombard a metal target, and use the accelerating p.d. to calculate the minimum wavelength of the X-rays produced
- understand how X-rays are used to image the internal structures of the body, including what is meant by contrast in X-ray imaging
- state and apply I = I₀e–μx when working with the attenuation of X-rays in matter
- understand that computed tomography (CT) scanning builds a 3D image of a structure inside the body in two stages: several X-ray images of one section, taken from different angles, are combined into a 2D image of that section; this is repeated at positions along an axis, and the 2D images of the sections are then combined
24.3PET scanning6 objectives
- understand that a tracer is, in essence, a substance in which radioactive nuclei are present, and that it may be put into the body and then absorbed by the tissue under investigation
- recall that a PET scan, short for positron emission tomography, uses a tracer that undergoes β+ decay
- understand that a particle and its antiparticle annihilate when they interact, with mass–energy and momentum both conserved in the process
- explain that during PET scanning, positrons released as the tracer decays are destroyed through annihilation upon encountering electrons in the tissue, which yields two gamma-ray photons moving in opposite directions
- work out the energy carried by each gamma-ray photon released when an electron-positron pair is annihilated
- understand that gamma-ray photons produced by an annihilation event leave the body, where detectors can pick them up, and that processing their arrival times creates an image showing the concentration of tracer in the tissue
25.1Standard candles4 objectives
- understand the meaning of luminosity: the overall power carried away as radiation from a star
- recall and use the inverse square law linking radiant flux intensity F to a source's luminosity L, given by F = L/(4πd²)
- understand that a body whose luminosity is known is termed a standard candle
- understand how standard candles are employed to work out how far away galaxies are
25.2Stellar radii3 objectives
- recall and apply Wien's displacement law, λmax ∝ 1/T, in order to approximate a star's peak surface temperature
- apply the Stefan–Boltzmann law in the form L = 4πσr²T⁴
- apply Wien's displacement law alongside the Stefan–Boltzmann law in order to approximate how large a star's radius is
25.3Hubble’s law and the Big Bang theory4 objectives
- understand that spectral lines, both emission and absorption, seen from far-off objects sit at longer wavelengths than their known values
- apply ∆λ / λ ≈ ∆f/f ≈ v /c when dealing with redshift in electromagnetic radiation, where the emitting object is travelling relative to the observer
- explain why the observed redshift suggests that the Universe is expanding
- state and apply Hubble’s law, v ≈ H₀d, and explain how this gives rise to the Big Bang theory (only SI units will be required)
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