OCR A A Level Physics.Paper 2

  "Electric Potential - CORRECT ANSWER The work done by an external force per unit positive charge to bring a charge from infinity to a point in an electrical field" "Electric Potential Difference - CORRECT ANSWER The work done by an external force per unit positive charge to move a charge between two points in an electrical field" "Similarities to Gravitational Fields - CORRECT ANSWER Both are radial fields, both follow an inverse square law" "Differences to Gravitational Fields - CORRECT ANSWER Gravitational fields are only attractive, electrical fields can be attractive and repulsive." "Capacitance - CORRECT ANSWER The charge stored per unit potential difference across a capacitor" "Capacitor - CORRECT ANSWER A component that stores charge, consisting of two plates separated by an insulator (dielectric)" "Farad - CORRECT ANSWER Unit for capacitance equivalent to CV-1. 1F is 1C of charge stored per volt." "Time constant - CORRECT ANSWER The product of capacitance and resistance, CR, for a capacitor-resistor circuit - equal to the time taken for the p.d. (or the current, or the charge) to decrease to e-1 (about 37%) of its initial value when the capacitor discharges through a resistor - symbol τ (tau), measured in seconds" "Exponential decay - CORRECT ANSWER A constant-ratio process in which a quantity decreases by the same factor in equal time intervals (fixed time intervals)" "Conservation of charge - CORRECT ANSWER A conservation law that states that electric charge cannot be created nor destroyed - total charge in any interaction must be the same before and after the interaction" "Law of capacitors in series - CORRECT ANSWER 1/C = 1/C1 + 1/C2 + ...." "Law of capacitors in parallel - CORRECT ANSWER C = C1 + C2 + ...." "radio - CORRECT ANSWER 10^3" "microwave - CORRECT ANSWER 10^-2" "Infrared - CORRECT ANSWER 10^-5" "visible - CORRECT ANSWER 0.5 x 10^-6" "ultraviolet - CORRECT ANSWER 10^-8" "x ray - CORRECT ANSWER 10^-10" "gamma ray - CORRECT ANSWER 10^-12" "Photon - CORRECT ANSWER A quantum of electromagnetic energy" "X-ray - CORRECT ANSWER Electromagnetic radiation with wavelength ranging from 0.1 to 10 nanometres" "x-ray tube - CORRECT ANSWER A piece of equipment that produces x ray photons by firing electrons from a beta cathode across a large PD in an evacuated tube-x ray photons are produced when the electrons are decelerated by hitting the target metal of the anode." "Thermionic emission - CORRECT ANSWER The release of electrons from the surface of a heated material" "Attenuation - CORRECT ANSWER The decrease of intensity of electromagnetic radiation as it passes through matter and/or space" "Attenuation coefficient - CORRECT ANSWER A measure of the absorption of x-ray photons by a substance. Also called absorption coefficient" "CAT scan - CORRECT ANSWER Computer Axial Tomography; x-ray images taken in a ring around the body to produce a composite 2d image" "Medical tracer - CORRECT ANSWER A compound labelled with a radioisotope that can be traced inside the body with a gamma camera" "Collimator - CORRECT ANSWER Part of a gamma camera, a honeycomb of long thin tubes made from lead that absorbs any photons arriving at an angle to the axis of the tubes so that a clear picture is obtained" "Scintillator - CORRECT ANSWER Part of a gamma camera, that produces thousands of visible photons when struck by a single gamma photon" "Photomultiplier tube - CORRECT ANSWER A piece of equipment that converts a photon of visible light into an electrical pulse" "PET scan - CORRECT ANSWER Positron emission tomography scan; forms an image from the 2 gamma rays produced during the annihilation of a positron and an electron" "Ultrasound - CORRECT ANSWER Sound that is higher frequency than the typical limit of human hearing (20kHz)" "Ultrasound transducer - CORRECT ANSWER A device used both to generate and to receive ultrasound which changes electrical energy into sound and sound into electrical energy" "Piezoelectric effect - CORRECT ANSWER When electric charge accumulates in a solid material due to an applied mechanical stress, producing a potential difference" "Acoustic impedance - CORRECT ANSWER The product of the density and the speed of ultrasound in a substance" "Intensity reflection coefficient - CORRECT ANSWER The ratio of reflected intensity to incident intensity at a boundary" "Coupling gel - CORRECT ANSWER A gel with acoustic impedance similar to that of skin smeared onto the transducer and the patient's skin before an ultrasounds scan in order to fill air gaps and ensure that almost all the ultrasound enters the patient's body" "Impedance matching - CORRECT ANSWER The use of two substances with similar acoustic impedance to minimise reflection of sound waves at the boundary" "Annihilation - CORRECT ANSWER The complete destruction of a particle and its anti particle in an interaction that releases energy in the form of identical photons" "Rest mass - CORRECT ANSWER The mass of a particle at rest" "Binding energy - CORRECT ANSWER The energy required to dissemble the nucleus of a particular isotope into its fundamental nucleons" "Mass defect - CORRECT ANSWER The difference in mass between a nucleus and its separated nucleons" "Binding energy per nucleon - CORRECT ANSWER The binding energy divided by the number of nucleons in the nucleus of an isotope" "Nuclear fission - CORRECT ANSWER A process in which a large nucleus splits into two smaller nuclei and two or three fast moving neutrons" "Induced fission - CORRECT ANSWER Fission caused by the absorption of another particle" "Nuclear fusion - CORRECT ANSWER A process in which two smaller nuclei join together to form one larger nucleus" "Thermal neutron - CORRECT ANSWER A neutron with the same amount of kinetic energy as the thermal energy of its surroundings - used to initiate fission reactions" "Chain reaction - CORRECT ANSWER A self propagating reaction - the products from one event are able to initiate the next" "Coolant - CORRECT ANSWER A fluid of a high specific heat capacity used to transfer heat from reaction chamber to the boiler" "Control rod - CORRECT ANSWER Absorbs excess neutrons in fission reaction to prevent/slow chain reaction in reactor core" "Moderator - CORRECT ANSWER Material in a nuclear reactor used to slow down rapidly moving neutrons enough so that they are able to initiate fission" "Beta decay - CORRECT ANSWER A process where a proton turns into a neutron and releases a high energy electron and an antineutrino, or where a neutron turns into a proton and releases a high energy positron and a neutrino" "Ionising radiation - CORRECT ANSWER Radiation that can ionise atoms by removing some of their electrons, leaving positive ions" "Radioactivity - CORRECT ANSWER The process by which unstable nuclei split or decay emitting ionising radiation (alpha, beta and gamma)" "Cloud chamber - CORRECT ANSWER A detector of ionising radiation consisting of a chamber filled with air, saturated with vapour at a very low temperature so that droplets of liquid condense around ionised particles left along the path of radiation" "Alpha radiation - CORRECT ANSWER Ionising radiation consisting of particles comprised of two protons and two neutrons" "Beta radiation - CORRECT ANSWER Ionising radiation consisting of fast moving electrons or positrons" "Gamma radiation - CORRECT ANSWER Ionising radiation consisting of high energy photons with wavelengths less than 10-13m which travel at the speed of light" "Parent nucleus - CORRECT ANSWER A nucleus before the occurrence of radioactive decay" "Daughter nucleus - CORRECT ANSWER A new nucleus formed following a radioactive decay" "Half-life - CORRECT ANSWER The time taken for half a sample of material to decay, or for the activity to decrease to half its original value" "Activity - CORRECT ANSWER Rate of decay" "Decay constant - CORRECT ANSWER The probability of decay of an individual nucleus per unit time" "Carbon-dating - CORRECT ANSWER A method for determining the age of organic material, by comparing the activities, or the ratios, of carbon 14 to carbon 12 nuclei of dead material of interest and similar living material" "Nucleus - CORRECT ANSWER Centre of an atom which is made up of neutrons and protons" "Nucleon - CORRECT ANSWER A proton or a neutron" "Nucleon number - CORRECT ANSWER The total number of protons and neutrons in the nucleus of an atom" "Proton number - CORRECT ANSWER The number of protons in the nucleus of an atom" "Isotopes - CORRECT ANSWER Isotopes are nuclei of the same element that have the same number of protons but different numbers of neutrons" "Atomic mass unit - CORRECT ANSWER One atomic unit is one-twelfth the mass of a neutral carbon-12 atom" "Strong nuclear force - CORRECT ANSWER One of the four fundamental forces in nature, acting on hadrons and holding nuclei together" "Weak nuclear force - CORRECT ANSWER One of the four fundamental forces in nature, acting on hadrons and leptons, responsible for inducing beta-decay." "Antiparticle - CORRECT ANSWER A particle with the same mass but opposite charge of another" "Positron - CORRECT ANSWER Anti electron (charge of +1e)" "Fundamental particle - CORRECT ANSWER A particle that has no internal structure and hence cannot be divided into smaller particles" "Hadron - CORRECT ANSWER A particle made up of quarks and which can take part in strong force interactions" Describe how ultrasound scanning is used to obtain diagnostic information about internal structures of a body. - CORRECT ANSWER -Pulses of ultrasound (sent into the body) -Wave / ultrasound / pulse / signal is reflected (at boundary of tissue) -Time of delay used to determine depth / thickness -The fraction of reflected signal is used to identify the tissue" "Describe the piezoelectric effect - CORRECT ANSWER The application of a p.d. across a material / crystal causes an expansion / contraction / vibration" "Describe the differences between an A-scan and a B-scan - CORRECT ANSWER -A-scan in one direction only / range or distance or depth finding -B-scan uses a number of sensors or a sensor in different positions / angles (to build up a 2D/3D image)" "Alpha-particle scattering experiment is... - CORRECT ANSWER evidence of a small, charged nucleus" "Simple nuclear model of the atom... - CORRECT ANSWER the atom is mostly space with a very small, very dense positively charged nucleus and negatively charged electrons located in the atomic space." "The relative size of the nucleus of an atom is... - CORRECT ANSWER 10^-15 (metres)" "The relative size of an alpha particle is... - CORRECT ANSWER 10^-10 (metres)" "The strong nuclear force... - CORRECT ANSWER acts between all nucleons. It is a short range force, effective over a few femtometres. Attractive above (approx.) 3fm and repulsive below (approx.) 0.5fm." "Radius of a nucleus - CORRECT ANSWER R = r0 A^(1/3), in which r0 is a constant and A is the nucleon number" "Rutherford Gold Foil Experiment Procedure - CORRECT ANSWER Pointed a beam of alpha particles at a thin foil of metal and measured the scattering pattern by using a fluorescent screen." "Rutherford Gold Foil Experiment Findings - CORRECT ANSWER 1. They spotted alpha particles bouncing off the metal foil in all directions, some right back at the source. 2. Only very few were deflected by large amounts (>90 degrees)" "Rutherford Gold Foil Experiment Conclusions - CORRECT ANSWER 1. The atom's positive charge was concentrated in a much tinier volume than Thomson imagined. 2. Tiny spheres of intense positive charge were separated by vast gulfs of empty space." "Lepton - CORRECT ANSWER Particles and antiparticles that do not experience the strong force. Including electrons, neutrinos and muons." "Quark - CORRECT ANSWER An elementary particle that can exist in six flavours, plus their antiparticles and joins with other quarks to make hadrons" "Meson - CORRECT ANSWER Hadrons made with a combination of a quark and an anti-quark" "Baryon - CORRECT ANSWER Hadrons made with a combination of three quarks or three anti-quarks" "Standard model - CORRECT ANSWER The current theory of particle physics, where the elementary particles consists of six quarks, six leptons, their antiparticles, and bosons for each of the four fundamental forces" "Magnetic field - CORRECT ANSWER The region of space in which a current or moving charge will experience a perpendicular magnetic force" "Right hand screw rule - CORRECT ANSWER A rule used determine the direction of the magnetic field lines that surround a current-carrying wire" "Flemming's left hand rule - CORRECT ANSWER A rule used determine the direction of the force acting on a current-carrying wire in a magnetic field:" "Thumb = force, First Finger= field(magnetic), second finger= current - CORRECT ANSWER " "Magnetic flux density - CORRECT ANSWER The strength of a magnetic field, defined by F/IL, F = force, I = current L= length" "Magnetic flux - CORRECT ANSWER The product of the component of the magnetic flux density perpendicular to a given area and that cross-sectional area" "Magnetic flux linkage - CORRECT ANSWER The product of the number of turns in a coil N, and the magnetic flux φ" "Faraday's law - CORRECT ANSWER The EMF induced by a changing magnetic field is directly proportional to the rate of change of magnetic flux linkage" "Lenz's law - CORRECT ANSWER The direction of the induced EMF or current is always such as to oppose the change producing it" "Point charge - CORRECT ANSWER An electric charge considered to exist at a single point, and thus having no volume" "Positive charge - CORRECT ANSWER One type of electric charge - positively charged objects attract negatively charged ones, and repel other positive charges" "Negative charge - CORRECT ANSWER One type of electric charge - negatively charged objects attract positively charged ones, and repel other negative charges" "Electric field - CORRECT ANSWER A region where a charged particle will experience an electric force" "Electric field strength - CORRECT ANSWER The force experienced per unit positive charge at that point" "Radial Field - CORRECT ANSWER A symmetrical field that diminishes with distance squared from its centre, such as the electrical field around a spherical charged object" "Coulomb's Law - CORRECT ANSWER Any two point charges exert an electrostatic (electrical) force on each other that is directly proportional to the product of their charges and inversely proportional to the square of their separation" "Quantisation - CORRECT ANSWER Some quantities, such as energy or charge, only being available in certain discrete values" "Electronvolt (eV) - CORRECT ANSWER A derived unit of energy defined as the energy transferred when an electron passes through a potential difference of 1 volt. 1 eV = 1.60 × 10-19J" "Planck constant - CORRECT ANSWER An important constant in quantum mechanics, which, among other things, is the constant of proportionality between photon energy and frequency" "Photoelectric effect - CORRECT ANSWER The emission of photoelectrons from the surface of a metal when electromagnetic radiation above the threshold frequency is incident on the metal" "Photoelectron - CORRECT ANSWER Electrons emitted from the surface of a metal by the photoelectric effect" "Threshold frequency - CORRECT ANSWER The minimum frequency of electromagnetic radiation that will cause the emission of a photoelectron from the surface of a particular metal" "Work function - CORRECT ANSWER The minimum energy needed to remove a single electron from the surface of a particular metal" "Stopping potential - CORRECT ANSWER The minimum potential difference required to reduce a photoelectron's velocity to zero" "Wave-particle duality - CORRECT ANSWER A theory that states that matter and electromagnetic radiation both have particle and wave properties, and display particle and wave behaviours" "De Broglie wavelength - CORRECT ANSWER The wavelength of a particle, calculated using the de Broglie equation" "Progressive wave - CORRECT ANSWER A wave that transfers energy from one place to another" "Longitudinal wave - CORRECT ANSWER A wave in which the direction of vibration is parallel to the direction of energy transfer" "Transverse wave - CORRECT ANSWER A wave in which the direction of vibration is perpendicular to the direction of energy transfer" "Displacement - CORRECT ANSWER The distance and direction of a point in the medium from its equilibrium position" "Amplitude - CORRECT ANSWER The magnitude of the maximum displacement of the medium" "Wavelength - CORRECT ANSWER The shortest distance between two points of equal phase on a progressive wave (e.g. distance from peak to adjacent peak)" "Period - CORRECT ANSWER The time for one complete oscillation of a particle in the medium" "Phase - CORRECT ANSWER How 'far through' a complete oscillation a point on the wave is, from 0° to 360° or from 0 rad to 2π rad" "Phase difference - CORRECT ANSWER The offset in phase between two points on the same wave or between two waves at a single point" "In phase - CORRECT ANSWER Particles oscillating completely in step with each other, phase difference 0 or 2π" "In antiphase - CORRECT ANSWER Particles oscillating completely out of step with each other, phase difference π" "Frequency - CORRECT ANSWER The number of complete waves passing a point per unit time or the number of oscillations completed by a point in the medium per unit time." "Wave speed - CORRECT ANSWER The speed of propagation of the wavefront, equal to the frequency × wavelength" "Wavefront - CORRECT ANSWER A line of points that are all in phase" "Reflection - CORRECT ANSWER A wave 'bounces' off a surface formed by the boundary between two different media (e.g. microwaves at an air/metal boundary). The angle of incidence is equal to the angle of reflection." "Refraction - CORRECT ANSWER A wave changes speed in traversing the boundary between two different media (e.g. light from air into glass). This leads to a change in wavelength (always) and a change in direction (unless the wave is propagating along the normal to the boundary)." "Diffraction - CORRECT ANSWER The spreading of a wave when it encounters a gap or obstacle (e.g. water waves passing through a harbour entrance)" "Polarisation - CORRECT ANSWER The restriction of the oscillations of transverse waves to one plane" "Intensity - CORRECT ANSWER The radiant power per unit area, proportional to amplitude squared" "Electromagnetic waves - CORRECT ANSWER Transverse waves with oscillating electric and magnetic field components and that do not need a medium to propagate" "Refractive index - CORRECT ANSWER The ratio of the speed of light in a vacuum to the speed of light through a medium" "Critical angle - CORRECT ANSWER The angle of incidence at a boundary that will produce an angle of refraction of 90°" "Total internal reflection - CORRECT ANSWER The reflection of all light when light hits a boundary at an angle greater than the critical angle" "Principle of superposition - CORRECT ANSWER When two waves meet at a point the resultant displacement is equal to the sum of the displacements of the original waves" "Interference - CORRECT ANSWER Superposition of two progressive waves to produce a result wave that follows the principle of superposition" "Constructive interference - CORRECT ANSWER Superposition of two waves that are in phase resulting in a larger amplitude" "Destructive interference - CORRECT ANSWER Superposition of two waves that are in antiphase resulting in a smaller amplitude" "Coherent - CORRECT ANSWER Two waves that have a constant phase difference" "Path difference - CORRECT ANSWER The difference in distance travelled by two waves from their sources to a specific point" "Stationary wave - CORRECT ANSWER A wave remains in a constant position and has no net transfer of energy along it" "Node - CORRECT ANSWER Points of zero amplitude on a stationary wave" "Antinode - CORRECT ANSWER Points of maximum amplitude on a stationary wave" "Fundamental frequency - CORRECT ANSWER The lowest frequency that an object can vibrate at" "Harmonic - CORRECT ANSWER An integer multiple of the fundamental frequency" "Parallel circuit - CORRECT ANSWER A type of branching electrical circuit in which there is more than one path for the current" "Internal resistance - CORRECT ANSWER The resistance of a power supply" "Terminal p.d. - CORRECT ANSWER Work done by charge carriers across a power source. Equal to emf when no current flows." "Lost volts - CORRECT ANSWER The p.d. lost due to the internal resistance" "Potential divider - CORRECT ANSWER An electrical circuit designed to divide the potential difference across two or more components in order to produce a specific output p.d." "Potentiometer - CORRECT ANSWER An electrical component with three terminals and some form of sliding contact that can be adjusted to vary the potential difference between the two terminals" "Potential difference (p.d.) - CORRECT ANSWER "The difference in electrical potential energy per unit charge between two points. Equal to the work done per unit charge by the charge carriers."" "Electromotive force (e.m.f) - CORRECT ANSWER "The electrical potential energy gained per unit charge passing through a cell or battery. Equal to the work done per unit charge on the charge carriers."" "Kirchhoff's Second Law - CORRECT ANSWER In any given loop in a circuit the sum of the EMFs is equal to the sum of potential differences. This is a consequence of the conservation of energy." "Thermionic emission - CORRECT ANSWER The production of electrons by heating up a metal" "Resistance - CORRECT ANSWER The potential difference require for one unit of current to flow through a component" "Ohm's Law - CORRECT ANSWER The current through a conductor is proportional to the potential difference across it (at constant temperature)" "Ohmic conductor - CORRECT ANSWER A conductor that follows ohm's law e.g. a fixed resistor" "Non-ohmic conductor - CORRECT ANSWER A conductor that does not follow ohm's law e.g. a filament lamp" "Resistivity - CORRECT ANSWER Defined by the equation ρ = RA / l where ρ is the resistivity, R is the resistance of the wire, A is its cross sectional area, l is its length" "Kilowatt-hour (kWh) - CORRECT ANSWER A unit of energy equal to 3.6×10⁶ J. The energy transferred by a 1kW device operating for 1 hour." "Power - CORRECT ANSWER The rate of energy transfer" "Light Dependent Resistor - CORRECT ANSWER A component, the resistance of which decreases with increasing intensity of illumination" "(NTC) thermistor - CORRECT ANSWER A component, the resistance of which decreases with increasing temperature" "Series circuit - CORRECT ANSWER A circuit in which all components are placed in the same continuous loop" "Electric current - CORRECT ANSWER The rate of flow of positive charge, usually measured in amperes" "Conventional current - CORRECT ANSWER Direction of flow of positive charge. It is the opposite direction to the flow of electrons" "Elementary charge, e - CORRECT ANSWER The charge on one proton, equal to 1.60×10-19C" "Relative charge - CORRECT ANSWER The charge of a particle measured in terms of the elementary charge, e" "Free electron - CORRECT ANSWER An electron in a metal that is not bound to an atom (delocalised) and is free to move" "Ion - CORRECT ANSWER An atom that has either lost or gained electrons and so has a net charge" "Anion - CORRECT ANSWER Negatively charged ions" "Cation - CORRECT ANSWER Positively charged ions" "Electrolyte - CORRECT ANSWER A liquid that contains ions that are free to move and so conducts electricity" "Conservation of charge - CORRECT ANSWER Charge cannot be created or destroyed" "Kirchoff's First Law - CORRECT ANSWER The sum of the currents entering any point in a circuit is equal to the sum of the currents leavening that point. It is effectively equivalent to the conservation of charge." "Number density, n - CORRECT ANSWER The number of free charge carriers per unit volume" "Insulator - CORRECT ANSWER A material that does not easily support an electric current due to having a high resistance and a very low number density" "Semiconductor - CORRECT ANSWER A material with an intermediate resistance and number density. The value of n can often be affected by temperature (e.g. thermistor) or illumination (e.g. LDR)" "Conductor - CORRECT ANSWER A material with a low resistance and a high number density" "Mean drift velocity - CORRECT ANSWER The average rate of change of displacement of a charge carrier attained due to an electric field" "