OCR A - AS Level Physics solutions with verified correct Answers 2025

What six base units of the SI system are used in A Level Physics? - Correct Answer metre, kilogram, second, Ampere, Kelvin, Mole What six base quantities of the SI system are used in A Level Physics? - Correct Answer length, mass, time, electric current, absolute temperature, amount of substance. What is the value of the prefix T (tera) - Correct Answer 10¹² What is the value of the prefix G (giga) - Correct Answer 10⁹ What is the value of the prefix M (mega) - Correct Answer 10⁶ What is the value of the prefix k (kilo) - Correct Answer 10³ What is the value of the prefix d (deci) - Correct Answer 10⁻¹ What is the value of the prefix c (centi) - Correct Answer 10⁻² What is the value of the prefix m (milli) - Correct Answer 10⁻³ What is the value of the prefix μ (micro) - Correct Answer 10⁻⁶ What is the value of the prefix n (nano) - Correct Answer 10⁻⁹ What is the value of the prefix p (pico) - Correct Answer 10⁻¹² What is the accuracy of measurements? - Correct Answer How close a measurements are to the true value. What is the precision of measurements? - Correct Answer How close to each other repeated measurements are. What is measurement error? - Correct Answer The difference between the measured value and the true value of the quantity. What are random errors? - Correct Answer Measurement errors that occur due to results varying in an unpredictable way. What is the main method for correcting for random errors? - Correct Answer Taking repeated measurements and finding the mean. What are systematic errors? - Correct Answer A measurement error that causes the measurements to differ from the true value by a consistent amount for each measurement. What is a zero error? - Correct Answer A systematic error that arises from an instrument reading reading a non-zero reading when nothing is being measured. What is an absolute uncertainty? - Correct Answer The interval around the measured value within which the true value is expected to lie. What is a percentage uncertainty? - Correct Answer The absolute uncertainty stated as a percentage of the measured value. How do you combine uncertainties when measurements are added or subtracted? - Correct Answer Add together the absolute uncertainties. How do you combine uncertainties when measurements are multiplied or divided? - Correct Answer Add together the percentage uncertainties. What happens to the uncertainty in a measurement when it is raised to a power? - Correct Answer The percentage uncertainty is multiplied by the power. What is a scalar quantity? - Correct Answer A quantity with magnitude but no direction. What is a vector quantity? - Correct Answer A quantity with magnitude and direction. When adding two perpendicular vectors what can you use to find the direction of the resultant? - Correct Answer Pythagoras' Theorem When adding two perpendicular vectors what can you use to find the magnitude of the resultant? - Correct Answer Trigonometry What is vector resolution? - Correct Answer The process of splitting a vector into two perpendicular components. What is a resultant vector? - Correct Answer The sum of two or more individual vectors. How is the resultant found in a vector diagram when adding several vectors together? - Correct Answer Join the vectors nose to tail and the resultant is from the tail of the first to the nose of the last vector. What is displacement? - Correct Answer The distance of an object from a point in a specific direction (vector) What is velocity? - Correct Answer Rate of change of displacement (vector) ∆s/∆t if constant What is speed? - Correct Answer Change in distance traveled per unit time (scalar) What is acceleration? - Correct Answer Rate of change of velocity (vector) ∆v/∆t if constant What are the units of acceleration? - Correct Answer ms⁻² What is meant by constant velocity? - Correct Answer Speed and direction of motion don't change What is represented by the gradient of a distance-time graph? - Correct Answer Speed What is represented by the gradient of a displacement-time graph? - Correct Answer Velocity What is represented by the gradient of a velocity-time graph? - Correct Answer Acceleration What is represented by the area under a velocity-time graph? - Correct Answer Change in displacement What is represented by the area under an acceleration-time graph? - Correct Answer Change in velocity When can the suvat equations by used? - Correct Answer When there is constant acceleration and motion along a straight line. What is the effect of mass on the acceleration for an object in free-fall? - Correct Answer None What is the relationship between displacement and time for an object falling freely from rest? - Correct Answer Displacement is proportional to time squared (sαt²) What is a projectile - Correct Answer An object acted upon only by the force of gravity What shape is the path of a projectile? - Correct Answer Parabolic What is the initial vertical velocity of an object projected horizontally? - Correct Answer Zero What angle of projection that results in maximum range - Correct Answer 45° Ignoring air resistance what is the acceleration of a projectile? - Correct Answer Always g downwards How does horizontal velocity vary in projectile motion? - Correct Answer It is constant If a projectile returns to its starting height - Correct Answer Initial and final velocities have the same magnitude What equation used for the horizontal component of projectile motion? - Correct Answer Displacement = Velocity x time (since horizontal velocity is constant) What aspect links the vertical and horizontal motion of a projectile - Correct Answer Time taken to fall Why can SUVAT equations can be used for the vertical component of projectile motion - Correct Answer Since the motion is in a single direction with a constant acceleration What is the vertical velocity at the peak of projectile motion? - Correct Answer Zero What is the centre of mass of an object? - Correct Answer The point at which the weight can be assumed to act. What does the weight of an object depend on? - Correct Answer It's mass and the gravitational field strength (W=mg) What is a free-body diagram? - Correct Answer It is a diagram showing the set of forces acting on a single object. What is weight? - Correct Answer The force due to gravity that acts through an objects centre of mass. What is friction? - Correct Answer The force that acts between two surfaces in contact to oppose motion. What is drag? - Correct Answer The resistive force that acts on an object moving through a fluid What is tension? - Correct Answer The force within a stretched object such as a cable or rope. What is upthrust? - Correct Answer The upward buoyant force that acts on an object in a fluid. What is a normal contact force? - Correct Answer A force that acts perpendicular to a surface when an object rests on it. How do you calculate the component of weight down a slope? - Correct Answer W sin (θ) where θ is the angle between the slope and horizontal. How do you calculate the component of weight acting perpendicular to a slope? - Correct Answer W cos (θ) where θ is the angle between the slope and horizontal. What are the key factors in determining the magnitude of drag force acting on an object in a fluid? - Correct Answer Speed and cross-sectional area What is terminal velocity? - Correct Answer The maximum speed reached by a falling object when drag and weight are equal. What is a moment? - Correct Answer The turning effect produced by a force. What units do moments have? - Correct Answer Nm How do you calculate a moment about a point? - Correct Answer Force x perpendicular distance to the line of action of the force What is meant by a body being in equilibrium? - Correct Answer The net force and the net moment acting on the body are both zero. What is the principle of moments? - Correct Answer For an object in rotational equilibrium the sum of the clockwise moments about any point is equal to the sum of anticlockwise moments about that point. What is a couple? - Correct Answer A pair of equal and opposite forces acting on an object with different lines of action. How do you calculate the moment of a couple? - Correct Answer Force x perpendicular distance between the lines of action of the forces. What is a triangle of forces? - Correct Answer A vector diagram of the three forces acting on an object in equilibrium. What is a resultant/net force? - Correct Answer The vector sum of forces acting on an object What is the density of a substance? - Correct Answer mass per unit volume. What are the units of density? - Correct Answer kgm⁻³ What is pressure? - Correct Answer Normal force acting per unit area What is Archimedes principle? - Correct Answer The upthrust exerted on an object is equal to the weight of fluid displaced, p = hg - Correct Answer What is work done equivalent to? - Correct Answer Energy Transferred What are the SI base units equivalent to the Joule? - Correct Answer kgm²s⁻² How is work done calculated? - Correct Answer W = F x cosΘ (distance moved x component of the force in the direction of motion) What is Θ in W = F x cosΘ? - Correct Answer The angle between the force and motion. What is energy? - Correct Answer The capacity of one object or system to do work (or cause a change) on another. What is represented by the are under a force-distance graph? - Correct Answer Work done. What is the principle of conservation of energy? - Correct Answer The energy of a closed system always remains constant. Energy can never be created or destroyed, only transferred. What form of energy is due to the motion of a mass? - Correct Answer kinetic energy What form of energy is due to the position of a mass in a gravitational field? - Correct Answer gravitational potential energy What form of energy is due to the bonds between atoms in a substance? - Correct Answer chemical energy What form of energy is due to the a reversible change in shape of an object? - Correct Answer elastic potential energy What form of energy is due to the position of a charge in an electric field? - Correct Answer electrical potential energy What form of energy is due to the forces between protons and neutrons in an atom? - Correct Answer Nuclear energy What form of energy is due to electromagnetic waves? - Correct Answer Radiant energy What form of energy is due to the mechanical wave motion of atoms? - Correct Answer Sound energy What form of energy is due to randomly distributed potential and kinetic energies of the atoms within a system? - Correct Answer Thermal energy What effect does friction have on the energy of a moving object? - Correct Answer Transfers kinetic energy primarily to thermal energy Describe the energy transformations for an object sliding downhill at constant speed. - Correct Answer Gravitational potential energy decreases at the same rate as work is done by friction. Describe the energy transformations for a vehicle travelling uphill at constant speed. - Correct Answer Work is being done by the driving force and the is equal to the gain in gravitational potential energy plus work done by friction What is power? - Correct Answer Power is the rate at which work is done P = W/t What is the derived unit of Power? - Correct Answer Watt (W) What are the equivalent SI base units of the Watt? - Correct Answer kgm²s⁻³ What is the equation P = Fv used for? - Correct Answer The power developed by an object moving at constant speed against a constant resistive force. How is % efficiency calculated? - Correct Answer (Useful output energy/total input energy) x 100 What is a tensile force? - Correct Answer A force produces an extension of the object. What is a compressive force? - Correct Answer A force that reduces the length of an object. What is Hooke's Law? - Correct Answer Force is proportional to extension so long as the elastic limit is not exceeded. What is elastic deformation? - Correct Answer When an object will return to its original shape when the load is removed. What is plastic deformation? - Correct Answer A permanent change in shape that remains once the load is removed. What is k in F = kx - Correct Answer The force constant. What are the units of force constant (k) - Correct Answer Nm⁻¹ What is represented by the area under a force-extension graph? - Correct Answer The work done stretching the object. What is meant by an elastic material? - Correct Answer A material which can be significantly deformed and will return to it's original shape. What is tensile stress? - Correct Answer The force applied per unit cross sectional area. What is tensile strain? - Correct Answer The fractional change in length of an object. What is a ductile material? - Correct Answer A material which ccan be drawn into a wire of hammered into thin sheets. What is the limit of proportionality of a material? - Correct Answer The point at which a material stops obeying Hooke's Law What is the elastic limit of a material? - Correct Answer The point at which a material starts to plastically deform. What is the yield point of a material? - Correct Answer The point at which the material starts to extend rapidly as stress increases. What is the ultimate tensile strength of a material? - Correct Answer The maximum stress a material can withstand before breaking. What is the breaking strength of a material? - Correct Answer The stress at the point of fracture. What is a strong material? - Correct Answer One with a high ultimate tensile strength. What are the units of Young Modulus? - Correct Answer Pa OR Nm⁻² When does the Young Modulus apply to a material? - Correct Answer When stress is proportional to strain OR when it is obeying Hooke's law How do you find the Young Modulus from a stress-strain graph? - Correct Answer The gradient of the initial straight line region. What material property does Young Modulus measure? - Correct Answer The stiffness. What is a brittle material? - Correct Answer A material the show only elastic behaviour up to its breaking point, without plastically deforming. What is a polymeric material? - Correct Answer A material made from long chain molecules. What is Newton's 1st Law of motion? - Correct Answer An object will remain at rest of move at a constant velocity unless acted upon by a resultant force What is Newton's 3rd Law of motion? - Correct Answer When two objects interact they exert forces on each other that are equal in magnitude, opposite in direction and of the same type of force. What is Newton's 2nd Law of motion? - Correct Answer Resultant force acting on an object is proportional to its rate of change of momentum, and is in the same direction. What two sets of units can be used for momentum? - Correct Answer Ns OR kgms⁻¹ How is the momentum of an object calculated? - Correct Answer Mass × velocity (p=mv) What is the principle of conservation of momentum? - Correct Answer The total momentum in a system of interacting objects is constant provided no external force acts. What is an elastic collision? - Correct Answer A collision in which kinetic energy is conserved What is an inelastic collision? - Correct Answer A collision in which some kinetic energy is transferred to other forms How is impulse calculated? - Correct Answer Force × time What is the relationship between impulse and momentum? - Correct Answer Impulse is equal to change in momentum. Area under a force time graph - Correct Answer Impulse Gradient of a momentum-time graph - Correct Answer Resultant force What is the change in momentum when an object of momentum p collides elastically at right angles with a wall? - Correct Answer -2p When can F=ma be used? - Correct Answer When an object has constant mass. What is electric current? - Correct Answer Rate of flow of charge. What is the Coulomb in base units? - Correct Answer AS What is a charge carrier? - Correct Answer A charged particle capable of transferring electric current. What do we mean when we say charge is quantised? - Correct Answer It can only take certain values (always ne) If n electrons are removed from a neutral object what is its charge? - Correct Answer ne What is an electrolyte? - Correct Answer A liquid containing charged ions. What is a metallic conductor? - Correct Answer A material comprising a lattice of positive ions and delocalised electrons that carry electrical current Which direction does conventional current flow? - Correct Answer From positive to negative. Which direction do electrons flow in a circuit? - Correct Answer From negative to positive. What is an ion? - Correct Answer A non-neutral atom or molecule. What is a cation? - Correct Answer A negatively charged ion. What is an anion? - Correct Answer A positively charged ion. What is an anode? - Correct Answer A positive electrode. What is a cathode? - Correct Answer A negative electrode. How is an ammeter connected? - Correct Answer In series What is the resistance of an ideal ammeter? - Correct Answer Zero. State Kirchoff's first law. - Correct Answer At any point in a circuit the sum of the currents entering that point is equal to sum of the currents leaving. What is n in the equation I = nAve and what are its units? - Correct Answer Number density of free charge carriers m⁻³ What is A in the equation I = nAve? - Correct Answer Cross-sectional area of the conductor. What is e in the equation I = nAve? - Correct Answer The elementary charge (1.6x10⁻¹⁹C) What is v in the equation I = nAve? - Correct Answer The drift velocity of the charge carriers. What is a conductor? - Correct Answer A material with a large number density of charge carriers ~10²⁸m⁻³ What is an insulator? - Correct Answer A material with a low number density of charge carriers. What is a semiconductor? - Correct Answer A material with an intermediate number density of charge carriers ~10¹⁷m⁻³ What is potential difference? - Correct Answer The work done per unit charge between two points What is the SI unit for potential difference? - Correct Answer Volt (V) What units are equivalent to the volt? - Correct Answer Joules per Coulomb (JC⁻¹ ) What is EMF (Electromotive force)? - Correct Answer The work done per unit charge supplied to the charge carriers How is a voltmeter connected? - Correct Answer In parallel. What is the resistance of an ideal voltmeter? - Correct Answer Infinite. What is thermionic emission? - Correct Answer The emission of electrons from the surface of a heated metal. What is the work done on an electron when it passes through a p.d. of V volts? - Correct Answer eV where e is the charge on the electron. What is Ohm's Law? - Correct Answer For a metallic conductor at constant temperature the p.d. is proportional to current. What is electrical resistance? - Correct Answer The opposition of an object to a flow of current through it. How is resistance calculated? - Correct Answer V/I What units are equivalent to an Ohm? - Correct Answer VA⁻¹ Why does resistance increases with temperature? - Correct Answer The amplitude of lattice ion vibrations increases causing more frequent collisions between electrons and lattice ions, leading to the electrons doingm more work as they move through the wire. Why does current flow lead to heating in components? - Correct Answer Electrons collide with the lattice ions and transfer some of their kinetic energy to the lattice ion's vibrations. What is an Ohmic conductor? - Correct Answer An object for which p.d. is proportional to current. What is meant by the threshold pd of a diode? - Correct Answer The pd at which resistance starts to fall rapidly as pd increases. What are the units of resistivity? - Correct Answer Ωm What is ρ in R = ρL / A? - Correct Answer The resitivity of the material. What is L in R = ρL / A? - Correct Answer The length of the wire. What is A in R = ρL / A? - Correct Answer The cross-sectional area of the wire As a metal gets hotter what happens to its resitivity? - Correct Answer It increases. What is meant by a negative temperature coefficient component? - Correct Answer One in which the resistance drops as temperature increases. Why does resistance of a thermistor fall as temperature increases? - Correct Answer The number density of charge carriers increases. What are thermistors commonly used in? - Correct Answer Temperature sensors. Why does the resistance of an LDR as light intensity changes? - Correct Answer Light increases the number density of charge carriers in the LDR. What are LDRs commonly used in? - Correct Answer Light intensity sensors. What happens to the resistance of an LDR as light intensity increases? - Correct Answer It decreases. What is a kilowatt-hour (kWh)? - Correct Answer The energy supplied when 1kW of power is supplied for 1 hour. How many Joules are equavlent to a kWh - Correct Answer 3.6MJ State Kirchoff's second law. - Correct Answer Sum of the EMFs is equal to the sum of the potential drops around a closed circuit loop. What law is Kirchoff's second law a consequence of? - Correct Answer Conservation of Energy What can we say about the current through components in series? - Correct Answer Same for each component What can we say about the current on different parallel branches? - Correct Answer It depends on the resistance of each branch. What can we say about the pd across parallel branches in a circuit? - Correct Answer It is the same for each branch How do find the total pd across several components in series? - Correct Answer It is equal to the sum of the pds across each component How do you find the total EMF from cells connected in series with the same polarity? - Correct Answer Their EMFs are added How do you find the total EMF from cells connected in series with opposite polarity? - Correct Answer The total EMF is the difference between their EMFs How do you calculate the total resistance of resistors in series? - Correct Answer Sum of the individual resistances What is the total resistance of n identical resistors in series? - Correct Answer n x R What is the total resistance of n identical resistors in parallel? - Correct Answer R ÷ n How do you calculate the resistance of resistors in parallel? - Correct Answer 1/RT=1/R1+1/R2... How does the total resistance change when a resistor is added in series? - Correct Answer It always increases How does the total resistance change when a resistor is added in parallel? - Correct Answer It always decreases What is the effect of connecting two identical resistors in parallel? - Correct Answer Resistance is halved What is the effect of connecting two identical resistors in series? - Correct Answer Resistance is doubled What is internal resistance? - Correct Answer The opposition to current created by the charge carriers having to flow through the source of EMF What are the lost volts for a power supply? - Correct Answer The pd dropped across the internal resistance OR the difference between the EMF and the terminal pd. What happens to the terminal pd of a source as the current supplied increases? - Correct Answer It falls due to the increasing lost volts to the internal resistance. How do you calculate lost volts for a supply? - Correct Answer Ir where r is the internal resistance. What is the relationship between EMF, terminal pd and lost volts? - Correct Answer EMF = terminal pd + lost volts How do you find the internal resistance from a graph or terminal pd against current? - Correct Answer -gradient How do you find the EMF from a graph or terminal pd against current? - Correct Answer y-intercept What is a potential divider? - Correct Answer Two or resitances in series with a fixed source of EMF. What determines the ratio of the pd across the resistors in a potential divider? - Correct Answer It is equal to the ratio of their resistances. How can a light sensor be made? - Correct Answer By creating a potential divider containing an LDR. How can a temperature sensor be made? - Correct Answer By creating a potential divider containing a thermistor. What component can be used to supply an adjustable output pd? - Correct Answer A potentiometer. What is a progressive wave? - Correct Answer A progressive wave that transfers energy through space. What is a transverse wave? - Correct Answer A wave in which the oscillations are perpendicular to the direction of wave propagation What is a longitudinal wave? - Correct Answer A wave in which the oscillations are parallel to the direction of wave propagation Give an example of a longitudinal wave - Correct Answer Sound, primary seismic waves Give an example of a transverse waves - Correct Answer Waves on a stretched string, secondary seismic waves, electromagnetic radiation What are the regions of high pressure in a longitudinal wave called? - Correct Answer Compressions What are the regions of low pressure in a longitudinal wave called? - Correct Answer Rarefactions What is the displacement of a wave? - Correct Answer The distance of a particle in the medium from it's equilibrium position in a particular direction. What is the equilibrium position in wave motion? - Correct Answer The position of the medium when undisturbed by a wave. What is the amplitude of a wave? - Correct Answer Maximum displacement of the medium from the equilibrium position. What is the frequency of a wave? - Correct Answer The number of wave cycles per second OR the number of waves passing a point per unit time What is the time period of a wave? - Correct Answer Time taken for one complete oscillation OR time for a whole wavelength to pass a fixed point. What is the relationship between frequency and time period? - Correct Answer f = 1/T or inverse proportionality How many radians of phase are there in one complete wave cycle? - Correct Answer 2π rad What term describes a phase difference of zero between two points on a wave? - Correct Answer In phase What term describes a phase difference of pi radians between two points on a wave? - Correct Answer In antiphase What is the phase difference between points half a wavelngth apart? - Correct Answer 180 degrees OR π rad What is the phase difference between points quarter of a wavelngth apart? - Correct Answer 90 degrees OR π/2 rad What is an oscillation? - Correct Answer A displacement one way and then the other about an equilibrium position. What is diffraction? - Correct Answer The spreading out of waves after passing through a slit/around an obstacle. What effect does reducing the size of a single slit have on diffraction? - Correct Answer Diffracted waves spread out more What is the effect of decreasing the wavelength on diffraction? - Correct Answer Diffracted waves spread out less What is meant by the intensity of a wave? - Correct Answer Intensity is the energy delivered by the wave per second per square metre normal to the wave How is the intensity of a wave related to the amplitude? - Correct Answer Intensity is proportional to amplitude squared. How does intensity vary with distance from a point source of waves? - Correct Answer Inverse square law or I = P / 4πr² What is a mechanical wave - Correct Answer A wave that requires a medium. What is the difference between mechanical waves and electromagentic waves? - Correct Answer EM waves don't require a medium. What is an electromagneitc wave? - Correct Answer An oscillation of the electric and magentic fields at right angles to each other. What is the speed of all EM waves in a vacuum/air? - Correct Answer 3x10⁸ms⁻¹ List the regions of the EM spectrum in order of incresasing wavelength. - Correct Answer Radio waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, Gamma rays Which two regions of the EM spectrum overlap? - Correct Answer X-rays and gamme rays. State the range of wavelengths (in powers of 10) of radio waves - Correct Answer >10⁻¹ State the range of wavelengths (in powers of 10) of microwaves - Correct Answer 10⁻¹ - 10⁻³ State the range of wavelengths (in powers of 10) of infrared - Correct Answer 10⁻³ - 10⁻⁶ State the range of wavelengths of visible light - Correct Answer 7x10⁻⁷ - 4x10⁻⁷ State the range of wavelengths (in powers of 10) of ultraviolet - Correct Answer 10⁻⁷ - 10⁻⁸ State the range of wavelengths (in powers of 10) of X-rays - Correct Answer 10⁻⁸ - 10⁻¹³ State the range of wavelengths (in powers of 10) of gamma rays - Correct Answer <10⁻¹⁰ Why can't longitudinal waves be polarised? - Correct Answer Longitudinal waves already only have a single driection of oscillation. What is the effect of a polarising filter? - Correct Answer It only transmits the component of the oscillations parallel to the filter What is the effect of perpendicular polarising filters - Correct Answer No light is transmitted Give a use of polarising filters. - Correct Answer LCD screens, 3D TV, polarimetry in manufacturing, anti-glare sunglasses What effect does reflection have on the polarisation of light? - Correct Answer Reflected light is partially polarised in the plane of the surface. What effect does scattering light have on polarisation? - Correct Answer Scattered light is polarised Which wave property always remains constant when a wave travels from one medium to another? - Correct Answer Frequency When entering a material with a higher refractive index what happens to wave speed? - Correct Answer decreases When entering a material with a lower refractive index what happens to wavelength? - Correct Answer increases What is the definition of the refractive index of a material - Correct Answer Speed of light in a vacuum/Speed of light in material What are the angles of incidence and refraction measured relative to? - Correct Answer The normal to the boundary Which way do waves refract when entering a material with a higher refractive index? - Correct Answer Toward the normal Which way do waves refract when entering a material with a lower refractive index? - Correct Answer Away from the normal What is the angle of refraction at the critical angle? - Correct Answer Ninety degrees What are the conditions required for total internal reflection? - Correct Answer "Wave must be travelling in a material with a higher index and meeting a boundary with a material of lower refractive index. The angle of incidence must be greater than the critical angle." - Correct Answer What two phenomena occur when a wave goes from a higher to a lower refractive index at an angle of incidence less than the critical angle? - Correct Answer The ray is refracted and partially reflected. What is the principle of superposition - Correct Answer When two waves meet at a point the resultant displacement is the (vector) sum of the displacements of the individual waves. What is constructive interference? - Correct Answer When two waves superpose in phase causing an increase amplitude. What is constructive interference? - Correct Answer When two waves superpose in antiphase causing a decreased amplitude. What are coherent sources of waves? - Correct Answer Sources that emit waves with a constant phase difference (and the same frequency). What is an interference pattern? - Correct Answer A pattern of regions of constructive and destructive interference produced by coherent sources of waves. What path difference is required for waves to be in phase? - Correct Answer A whole number of wavelengths What path difference is required for waves to be in antiphase? - Correct Answer An odd number of half wavelengths What is the relationship between path difference and phase difference for coherent sources? - Correct Answer (Path difference/wavelength) x 2π What term describes a phase difference of zero between two waves? - Correct Answer In phase What term describes a phase difference of π radians between two waves? - Correct Answer In antiphase What is x in the double slit equation (λ = ax/D)? - Correct Answer Fringe seperation What is D in the double slit equation (λ = ax/D)? - Correct Answer Distance between the double slits and the screen What is a in the double slit equation (λ = ax/D)? - Correct Answer Distance between the double slits What occurs to cause a dark fringe in the double slit experiment? - Correct Answer Destructive interference of the light from each slit What occurs to cause a bright fringe in the double slit experiment? - Correct Answer Constructive interference of the light from each slit What did Young's double slit experiment demonstrate about the nature of light? - Correct Answer That light exhibits wave behaviour. What name is given to light of a single frequency/wavelength? - Correct Answer Monochromatic Why did Young place a single slit before the double slit? - Correct Answer To ensure the light from each of the double slits was in phase. What are the condition required for a stationary wave to form? - Correct Answer Two waves travelling/propagating in opposite directions superpose with the same frequency and similar amplitudes What is an antinode on a stationary wave? - Correct Answer A point where the progressive waves are in phase and constructively interfering resulting in maximum amplitude What is an node on a stationary wave? - Correct Answer A point where the progressive waves are in antiphase and are destructively interfering resulting in minimum amplitude How many wavelengths are there between adjacent nodes? - Correct Answer Half a wavelength What is the phase difference between points either side of a node? - Correct Answer Pi Rad/180 degrees What is the phase difference of points between two adjacent nodes? - Correct Answer Zero How does phase vary along a progressive wave? - Correct Answer Changes continuously across each wave cycle. How does amplitude vary in a stationary wave? - Correct Answer It varies continuously along the wave. It is a maximum at antinodes and a minimum at nodes. How does amplitude vary in a progressive wave? - Correct Answer It is the same at every point along the wave. What type of wave doesn't tranfer energy? - Correct Answer Stationary waves What is the fundamental frequency of a string? - Correct Answer The lowest frequency which produces a stationary wave on the string. What factors determine the fundamental frequency on a string - Correct Answer Length, tension and the thickness of the string. What determines the pitch produced by a stationary wave in a musical instrument? - Correct Answer The frequency of the 1st harmonic What determines the loudness of sound? - Correct Answer The amplitude of the sound wave Why can only certain frequency stationary waves be produced on a stretched string? - Correct Answer There must be nodes at the fixed ends and only certain frequencies/wavelengths allow this. What feature of a stationary wave is always formed at an open end of a tube? - Correct Answer (Displacement) Antinode What feature of a stationary wave is always formed at a closed end of a tube? - Correct Answer (Displacement) Node What determines the energy of a photon? - Correct Answer The frequency/wavelength What is a photon? - Correct Answer A quantum of energy of electromagnetic radiation How do you calculate the energy of a photon? - Correct Answer E = hf OR E =hc/λ What is an electron volt? - Correct Answer The energy gained or lost by an electron passing through a potential difference of 1V How do convert from eV to J? - Correct Answer multiply by 1.6x10^-19 How do convert from J to eV? - Correct Answer divide by 1.6x10^-20 What is the threshold p.d. of an LED? - Correct Answer The minimum potential difference required for the LED to produce light. How can the threshold p.d. of an LED be used to find photon energy? - Correct Answer The energy transferred by the electrons (e x V) is equal to the energy of the photons produced (hf). What is the photoelectric effect? - Correct Answer The emission of electrons from a metal surface when illuminated with light. What is the atomic structure of a metal? - Correct Answer A lattice of positive ions surrounded by a sea of free electrons. What is a photoelectron? - Correct Answer An electron that has been removed from a metal by absorbing a photon What is the work function? - Correct Answer The minimum energy required to remove an electron from the surface of a metal What is the threshold frequency? - Correct Answer The minimum frequency of light required to produce photoelectrons from a metal What is monochromatic light - Correct Answer Light of a single frequency/wavelength What is the relationship between work function and threshold frequency? - Correct Answer ∅ = hf₀ What is required for a photon to be able to produce photoelectrons? - Correct Answer Its frequency is greater than the threshold frequency Why can't light sources below the threshold frequency produce photoelectrons? - Correct Answer The photon energy is less than the work function How do photons and electrons interact? - Correct Answer A single photon can be absorbed/emitted by a single electron which gains/loses the energy of the photon. What is the effect on an electron of absorbing a photon? - Correct Answer The electron gains the energy of the photon What effect does increasing the frequency of a monochromatic light source have on photoelectrons produced? - Correct Answer Photoelectrons will have a greater maximum kinetic energy What is the effect of increasing the intensity of a monochromatic light source on photoelectrons produced? - Correct Answer More photoelectrons will be produced but they will have the same maximum kinetic energy Why does the kinetic energy of photoelectrons from monochromatic light vary in the photoelectric effect? - Correct Answer The work function is a minimum energy. Some electrons are liberated from deeper into the metal and require more energy to be liberated. What two factors that determine the maximum kinetic energy of photoelectrons? - Correct Answer The frequency of the light and the work function of the metal What determines the rate at which energy is delivered by a wave? - Correct Answer Intensity/amplitude of the wave What is hf in Einstein's photoelectric effect equation (hf =