Exam (elaborations) physics for the year 2025 with correct answers

AQA GCSE Physics - Paper 2 The momentum of one thing is always equal to the momentum of another thing e.g. a skateboarder has the same momentum as the skateboard" "Equation for Momentum - CORRECT ANSWER Momentum (kg m/s) = mass (kg) x velocity (m/s) p=mv" "What is the conservation of momentum? - CORRECT ANSWER In a closed system, the total momentum before an event is the same as after the event" "What is a closed system? - CORRECT ANSWER When no external forces act" "Equation for Force 2 - CORRECT ANSWER Force (N) = Mass (kg) x Acceleration (m/s²) F=ma" "Equation for Force 3 - CORRECT ANSWER Force (N) = Change in momentum (kg m/s) / Change in time (s) F=mΔv/Δt" What are vectors? - CORRECT ANSWER Quantities that have a magnitude and a direction" "What are scalars? - CORRECT ANSWER Quantities that only have a magnitude" "Examples of vectors - CORRECT ANSWER Force Velocity Displacement Acceleration Momentum" "Examples of scalars - CORRECT ANSWER Speed Distance Mass Temperature Time" "What are contact forces? - CORRECT ANSWER Forces that act when two objects are touching" "What are non-contact forces? - CORRECT ANSWER Forces that act without the need for two objects to be touching" "Examples of contact forces - CORRECT ANSWER Friction Air resistance Tension in ropes Normal contact force" "Examples of non-contact forces - CORRECT ANSWER Magnetic force Gravitational force Electrostatic force" "What is mass? - CORRECT ANSWER The amount of material an object is made of It is the same value everywhere Measured using a mass balance" "What is weight? - CORRECT ANSWER The force acting on an object due to gravity It depends on the strength of the gravitational field at the location of the object Measured using a calibrated spring balance - newtonmeter" "Equation for Weight - CORRECT ANSWER Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg) W=mg" "What is weight directly proportional to? - CORRECT ANSWER Mass" "What are free body diagrams? - CORRECT ANSWER Diagrams that show all the forces acting on an object" "What is the minimum number of forces acting on an object in real situations? - CORRECT ANSWER At least 2 forces" "What is the resultant force? - CORRECT ANSWER The single force that replaces multiple forces acting at a single point" "How is work done? - CORRECT ANSWER When a force moves an object through a distance, energy is transferred and work is done on the object" "Equation for 'Work Done' - CORRECT ANSWER Work done (J) = Force (N) x Distance (m) W=Fs" "What is 1J equal to? - CORRECT ANSWER 1Nm" "What could happen when you apply a force to an object? - CORRECT ANSWER It may stretch, compress or bend" "Journey of a parachutist - CORRECT ANSWER 1) When they first start falling, the gravitational force is greater than the air resistance, thus he accelerates 2) As he continues to accelerate, the air resistance increases & the acceleration is reduced 3) Eventually, the air resistance will equal his weight - has now reached terminal velocity 4) From this point, he continues to fall at constant speed" "How does a parachute reduce terminal velocity? - CORRECT ANSWER Opening a parachute will increase the surface area, thus it causes air resistance to increase so that it is greater than the weight - the parachutist will fall more slowly" "What is a fluid? - CORRECT ANSWER A substance that flows easily - either a liquid or a gas" "What do waves do? - CORRECT ANSWER They transfer energy in the direction they are travelling" "Equation for the Period of a Wave - CORRECT ANSWER Period (s) = 1/Frequency (Hz) T=1/f" "What is the amplitude? - CORRECT ANSWER The maximum displacement of a point on the wave from its undisturbed position" "What is the wavelength? - CORRECT ANSWER The distance between the same point on two adjacent waves (between the trough of one wave and the trough of the wave next to it)" "What is the frequency? - CORRECT ANSWER The number of waves passing a certain point per second 1Hz is one wave per second" "What is the crest? - CORRECT ANSWER The top point of a wave" "What is the trough? - CORRECT ANSWER The bottom point of a wave" "Transverse waves - CORRECT ANSWER The oscillations (vibrations) are perpendicular to the direction of energy transfer Most waves are transverse e.g. 1) All electromagnetic waves e.g. light 2) Ripples and waves in water 3) A wave on a string" "Longitudinal waves - CORRECT ANSWER The oscillations are parallel to the direction of energy transfer Examples are: 1) Sound waves in air, ultrasound 2) Shock waves e.g. some seismic waves" "What is the wave speed? - CORRECT ANSWER The speed at which energy is being transferred or the speed at which the wave is moving at" "Equation for Wave Speed - CORRECT ANSWER Wave Speed (m/s) = Frequency (Hz) x Wavelength (m) v=fλ" "What is the speed of sound in air? - CORRECT ANSWER 330m/s" "What does an oscilloscope do? - CORRECT ANSWER Along with two microphones, it is used to find the wavelength of sound waves" "What happens when waves arrive at a boundary between two different materials? - CORRECT ANSWER 1) The waves are absorbed by the material the wave is trying to cross into - transfers energy to the material's energy stores 2) The waves are transmitted - they carry on travelling through the new material (often leads to refraction) 3) The waves are reflected" "Rule for all reflected waves - CORRECT ANSWER Angle of incidence = angle of reflection" "What is the angle of incidence? - CORRECT ANSWER The angle between the incoming wave and the normal" "What is the angle of reflection? - CORRECT ANSWER The angle between the refracted wave and the normal" "What is the normal? - CORRECT ANSWER An imaginary line that's perpendicular to the surface at the point of incidence" "What is a specular reflection? - CORRECT ANSWER This happens when a wave is reflected in a single direction by a smooth surface E.g. when light is reflected by a mirror, you get a nice, clear reflection" "What is a diffuse reflection? - CORRECT ANSWER When a wave is reflected by a rough surface & the reflected rays are scattered in lots of different directions - happens due to the normal being different for each incoming ray, therefore the angle of incidence is different for each ray" "Length of a radio wave - CORRECT ANSWER 1m-10⁴m" "Length of a microwave - CORRECT ANSWER 10⁻²m" "Length of a infrared wave - CORRECT ANSWER 10⁻⁵m" "Length of a visible light wave - CORRECT ANSWER 10⁻⁷m" "Length of an ultraviolet wave - CORRECT ANSWER 10⁻⁸m" "Length of an x-ray - CORRECT ANSWER 10⁻¹⁰m" "Length of a gamma ray - CORRECT ANSWER 10⁻¹⁵m" "EM continuous spectrum - CORRECT ANSWER 1) Radio waves 2) Microwaves 3) Infrared waves 4) Visible light rays 5) Ultraviolet waves 6) X-rays 7) Gamma rays" "What is refraction? - CORRECT ANSWER When a wave crosses a boundary between materials at an angle, it will change direction" "What affects the rate of refraction? - CORRECT ANSWER How much the wave speeds up/slows down - this depends on the density of the two materials If the wave slows down, it will bend towards the normal If the wave speeds up, it will bend away from the normal" "What happens during reFraction? - CORRECT ANSWER The wavelength of a wave changes but the frequency stays the same" "What is optical density? - CORRECT ANSWER A measure of how quickly light can travel through a material - the higher the optical density, the slower light waves travel through it" "What are EM waves made up of? - CORRECT ANSWER Oscillating electric and magnetic fields" "How are EM waves produced? - CORRECT ANSWER Alternating currents are made up of oscillating charges - as the charges oscillate, they produce oscillating electric & magnetic fields i.e. EM waves" "What is the frequency of waves equal to? - CORRECT ANSWER The frequency of the alternating current they were produced from" "Why do objects sink? - CORRECT ANSWER The object's weight is more than the upthrust It has a high density" "Low density - CORRECT ANSWER If an object is less dense than the fluid it is placed in, it weighs less than the equivalent volume of fluid It will displace a volume of fluid that is equal to its weight before it is completely submerged" "High density - CORRECT ANSWER If an object is denser than the fluid it is placed in, it will be unable to displace enough fluid to equal its weight, therefore its weight will be larger" "How do submarines make use of upthrust? - CORRECT ANSWER To sink, large tanks are filled with water to increase the weight of the submarine so that it is more than the upthrust To float, the tanks are filled with compressed air to reduce the weight so that it is less than the upthrust" "What is atmospheric pressure? - CORRECT ANSWER A layer of air that surrounds Earth It's created on a surface when air molecules collide with the surface" "What is atmospheric pressure inversely proportional to? - CORRECT ANSWER Altitude (height above Earth) If the altitude increases, atmospheric pressure decreases and becomes less dense" "What else happens when altitude increases? - CORRECT ANSWER There are fewer air molecules above a surface as the height increases, therefore the weight of the air above it (which contributes to atmospheric pressure) decreases" "What is distance? - CORRECT ANSWER How far an object has moved" "What is displacement? - CORRECT ANSWER It measures the distance and direction in a straight line from an object's starting point to its finishing point" "What is speed? - CORRECT ANSWER How fast you're going" "What is velocity? - CORRECT ANSWER Speed (how fast you're going) in a given direction" "Equation for Speed - CORRECT ANSWER Distance Travelled (m) = Speed (m/s) x Time (s) s=vt" "What is the typical speed of a person walking? - CORRECT ANSWER 1.5m/s" "What is the typical speed of a person running? - CORRECT ANSWER 3m/s" "What is the typical speed of a person cycling? - CORRECT ANSWER 6m/s" "What is the typical speed of a car? - CORRECT ANSWER 25m/s" "What is the typical speed of a train? - CORRECT ANSWER 55m/s" "What is the typical speed of a plane? - CORRECT ANSWER 250m/s" "What factors affect speed? - CORRECT ANSWER Fitness of the person Age of the person Distance travelled Terrain Climate Gender of the person" "What factors affect wind speed? - CORRECT ANSWER Temperature Atmospheric pressure Any large buildings or structures nearby e.g. forests reduce wind speed travelling through them" "What is acceleration? - CORRECT ANSWER The change in velocity in a certain amount of time" "Equation for Acceleration - CORRECT ANSWER Acceleration (m/s²) = Change in Velocity (m/s) / Time (s) a=Δv/t" "What is deceleration? - CORRECT ANSWER Negative acceleration - when something slows down, the change in velocity is negative" "What is constant acceleration? - CORRECT ANSWER Uniform acceleration - acceleration due to gravity is uniform for objects in free fall 9.8m/s² near the Earth's surface" "Equation for Uniform Acceleration - CORRECT ANSWER Final velocity² (m/s) - Initial velocity² (m/s) = 2 x Acceleration (m/s²) x Distance (m) v²-u²=2as" "Distance-Time Graphs - Features - CORRECT ANSWER 1) Gradient = speed 2) Flat sections = object is stationary 3) Straight uphill sections = object is travelling at a steady speed 4) Curves = object is accelerating or decelerating 5) Steepening curve = object is speeding up 6) Levelling off curve = object is slowing down" "Velocity-Time Graphs - Features - CORRECT ANSWER 1) Gradient = acceleration 2) Flat sections = object is travelling at a steady speed 3) Uphill sections = object is accelerating 4) Downhill sections = object is decelerating 5) Curves = object is changing acceleration The steeper the graph, the greater the acceleration or deceleration" "What does friction do? - CORRECT ANSWER It causes objects to slow down when they rub against another surface It always acts in the opposite direction to movement It's always smaller than the driving force" "Where do you get friction? - CORRECT ANSWER When two surfaces are in contact or when an object passes through a fluid (drag)" "What is drag? - CORRECT ANSWER The resistance you get in a fluid Air resistance is a type of drag" "How do you reduce drag? - CORRECT ANSWER Keep the shape of an object streamlined" "Process of a falling object - CORRECT ANSWER 1) When a falling object first sets off, the force of gravity is much more than the frictional force slowing it down, therefore the object accelerates 2) As the speed increases, the friction builds up 3) The acceleration is gradually reduced until eventually, the friction force is equal to the accelerating force - the resultant force is 0 4) At this point, it will have reached maximum speed or terminal velocity and will fall at a steady speed" "What does air resistance do? - CORRECT ANSWER It causes things to fall at different speeds" "What determines the terminal velocity? - CORRECT ANSWER The terminal velocity of any object is determined by its drag in comparison to its weight" "What affects the frictional force? - CORRECT ANSWER The shape and area of an object" "Newton's First Law - Law of Inertia - CORRECT ANSWER If the resultant force on a stationary object is zero, the object will remain stationary If the resultant force on a moving object is zero, it will just carry on moving at the same velocity" "What does a non-zero resultant force always produce? - CORRECT ANSWER Acceleration or deceleration in the direction of the force" "Which forms does acceleration take on? - CORRECT ANSWER 1) Starting 2) Stopping 3) Speeding up 4) Slowing down 5) Changing direction" "Newton's Second Law - CORRECT ANSWER Force ∝ Acceleration Acceleration is inversely proportional to the mass of an object F=ma" "What is inertia? - CORRECT ANSWER When objects continue in the same state of motion before they are acted upon by a resultant force" "What is the inertial mass? - CORRECT ANSWER It measures how difficult it is to change the velocity of an object It's the ratio of force over acceleration" "Newton's Third Law - CORRECT ANSWER When two different objects interact, the forces they exert on each other are equal and opposite An action always has an equal and opposite reaction" "What is equilibrium? - CORRECT ANSWER When two different forces are equal when acting on the same object E.g. a book resting on the ground is in equilibrium - the weight of the book is equal to the normal contact force" "Equation for Stopping Distance - CORRECT ANSWER Stopping Distance = Thinking Distance + Braking Distance" "What is the thinking distance? - CORRECT ANSWER How far the car travels during the driver's reaction time" "What is the braking distance? - CORRECT ANSWER The distance taken to stop under the braking force" "Typical car braking distances - CORRECT ANSWER 14m at 30mph 55m at 60mph 75m at 70mph" "What is thinking distance affected by? - CORRECT ANSWER 1) Speed - the faster you're going, the further you'll travel during your reaction time 2) Your reaction time - the longer it is, the longer your thinking distance 3) Alcohol 4) Drugs 5) Sleep deprivation 6) Distractions" "What is braking distance affected by? - CORRECT ANSWER 1) Speed - the faster a vehicle travels, the longer it takes to stop 2) Weather/Road surface - if it's wet or icy, there is less grip (and less friction) between a vehicle's tyres and the road, which can cause tyres to skid 3) Condition of tyres - if the tyres are bald, then they cannot get rid of water in wet conditions, thus leading to skidding on top of the water 4) Quality of brakes - if brakes are worn or faulty, they won't be able to apply as much force as well-maintained brakes, which could be dangerous when wanting to brake hard" "What happens when the brake pedal is pushed? - CORRECT ANSWER The brake pads are pressed onto the wheels, thus causing friction, which causes work to be done. The work done between the brakes and the wheels transfers energy from the kinetic energy stores of the wheels to the thermal energy stores of the brakes, which as a result, increase in temperature" "What happens when a vehicle is going really fast? - CORRECT ANSWER It has more energy in its kinetic energy stores, so the more work needs to be done to stop it - a greater braking force will be needed to make the vehicle stop within a certain distance, therefore the deceleration will be larger The larger the deceleration, the more dangerous it will be as the brakes could overheat or cause the vehicle to skid" "What is the typical reaction time? - CORRECT ANSWER Between 0.2s and 0.9s" "Typical thinking distances - CORRECT ANSWER 30mph - 9m 50mph - 15m 70mph - 21m" "Typical space needed to be left for stopping distances - CORRECT ANSWER 30mph - 6 car lengths 50mph - 13 car lengths 70mph - 24 car lengths" "What is momentum? - CORRECT ANSWER How much 'oomph' an object has All moving objects have it "What happens when an object is inelastically deformed? - CORRECT ANSWER The object won't return to its original shape and length after the force has been removed" "Equation for Force 1 - CORRECT ANSWER Force (N) = Spring Constant (N/m) x Extension (m) F=ke" "What is extension directly proportional to? - CORRECT ANSWER The force applied F∝e" "The stiffer the spring... - CORRECT ANSWER ...The greater the spring constant" "What is the limit of proportionality? - CORRECT ANSWER The point at which extension is no longer directly proportional to force" "Equation for 'Moments' - CORRECT ANSWER Moment of a force (Nm) = Force (N) x Distance (m) M=Fd" "What is a moment? - CORRECT ANSWER The turning effect of a force" "When will an object not turn? - CORRECT ANSWER When the object is balanced - the total anticlockwise moment equals the total clockwise moment about a pivot" "What affects the size of a moment? - CORRECT ANSWER 1) The size of the force applied - a larger force will produce a larger moment 2) The perpendicular distance from the pivot to the line of action of the force - any angle smaller than 90° will result in a smaller distance, thus a smaller moment" "What do levers do? - CORRECT ANSWER They increase the distance from the pivot at which the force is applied" "Do levers make it easier or harder to do work? - CORRECT ANSWER Easier to do work" "What are gears and what do they do? - CORRECT ANSWER Circular discs with 'teeth' around their edges Their teeth interlock so that turning one causes another to turn in the opposite direction They are used to transmit the rotational effect of a force from one place to another" "What is pressure? - CORRECT ANSWER The force per unit area" "Equation for Pressure - Surface of a fluid - CORRECT ANSWER Pressure (Pa) = Force normal to a surface (N) / Area of that surface (m²) p=F/A" "What is the pressure of a fluid? - CORRECT ANSWER A force is exerted normal (at right angles) to any surface in contact with the fluid" "What is density? - CORRECT ANSWER A measure of the 'compactness' of a substance" "Equation for Pressure - Liquid - CORRECT ANSWER Pressure (Pa) = Height of the column of liquid (the depth)(m) x Density of the liquid (kg/m³) x Gravitational field strength (N/kg) p=hρg" "What is upthrust? - CORRECT ANSWER The force exerted on the bottom of the object is larger than the force acting on the top of the object - the resultant force upwards on an object when it is submerged in water" "What is upthrust equal to? - CORRECT ANSWER The weight of fluid that has been displaced by the object" "Why do objects float? - CORRECT ANSWER The upthrust of the object is equal to the object's weight, thus the force balances It has a low density" "Safety Features of Cars - CORRECT ANSWER 1) Crumple zones crumple on impact, increasing the time taken for the car to stop 2) Seat belts stretch slightly, increasing the time taken for the wearer to stop 3) Air bags inflate before you hit the dashboard of a car. The compressing air inside it slows you down more gradually than if you had just hit the hard dashboard" "Bike Safety - CORRECT ANSWER Bike helmets contain a crushable layer of foam which helps to lengthen the time taken for your head to stop in a crash - reduces the impact on your brain" "Crash mats safety - CORRECT ANSWER Crash mats and cushioned playground flooring increase the time taken for you to stop if you fall on them - they are made from soft, compressible materials" "Investigating Springs - Method - CORRECT ANSWER 1) Measure the natural length of the spring with a millimetre ruler clamped to the stand. Ensure you take the reading at eye level & add a marker to the bottom of the spring to make the reading more accurate 2) Add a mass to the spring & allow it to come to rest. Record the mass & measure the new length of the spring. The extension is the change in length 3) Repeat this process until you have enough measurements - no fewer than 6 4) Plot a force-extension graph of your results - it will start to curve if you exceed the limit of proportionality" "Investigating Motion - Method - CORRECT ANSWER 1) Set up the apparatus. Set up the trolley so it holds a piece of card with a gap in the middle that will interrupt the signal on the light gate twice. If you measure the length of each bit of card that will pass through the light gate & input this into the software, the light gate can measure the velocity for each bit of card - can use this to work out the trolley's acceleration 2) Connect the trolley to a piece of string that goes over a pulley & is connected on the other side to a hook 3) The weight of the hook & any masses attached to it will provide the accelerating force, equal to the mass if the hook x acceleration due to gravity 4) The weight of the hook & masses accelerates both the trolley & the masses, so you're investigating the acceleration of the system 5) Mark a starting line on the table the trolley is on so that the trolley always travels the same distance to the light gate 6) Place the trolley on the starting line, holding the hook so the string is taut, and release it 7) Record the acceleration measured by the light gate as the trolley passes through it - acceleration of the whole system 8) Repeat twice more to get an average" "Investigating the Effect of Mass on Acceleration - CORRECT ANSWER Add masses to the trolley one at a time to increase the mass of the system. Don't add masses to the hook, or you'll change the force. Record the average acceleration for each mass" "Investigating the Effect of Force on Acceleration - CORRECT ANSWER Keep the total mass of the system the same, but change the mass on the hook. Start with all the masses loaded onto the trolley, and transfer the masses to the hook one at a time, to increase the accelerating force. The mass of the system stays the same as you're only transferring the masses from one part of the system to another. Record the average" "Why do you weigh more on a bigger planet? - CORRECT ANSWER There is a stronger gravitational pull towards the planet's centre" "What is hydraulic pressure? - CORRECT ANSWER The pressure that is caused by a liquid Pressure in a liquid is caused by the weight of the air above it" "Pressure in a liquid - CORRECT ANSWER 1) Acts in all directions 2) Increases with depth" "What is terminal velocity? - CORRECT ANSWER The constant speed that a freely falling object eventually reaches when the air resistance prevents further acceleration" "What effects does gravity produce when it attracts all masses? - CORRECT ANSWER 1) On the surface of a planet, it makes all things fall towards the ground 2) It gives everything a weight" "What happens when an object has been elastically deformed? - CORRECT ANSWER It can return to its original shape and length after the force has been removed All energy is transferred to the object's elastic potential energy store" "How are radio waves produced? - CORRECT ANSWER They are produced using an alternating current in an electrical circuit When transmitted radio waves reach a receiver, the radio waves are absorbed. The energy carried by the waves is transferred to the electrons in the material of the receiver. This energy causes the electrons to oscillate & if the receiver is part of a complete electrical circuit, it generates an alternating current - this current will have the same frequency as the radio waves that generated it" "Radio Waves - CORRECT ANSWER EM radiation with wavelengths longer than 10cm Long-wave radio signals can be transmitted long distances - they diffract around the curved surface of the Earth, thus they can be received even if the receiver isn't in the line of sight of the transmitter Short-wave radio signals (10m-100m) can be received at long distances - they are reflected from the ionosphere Medium-wave signals can also reflect from the ionosphere, depending on atmospheric conditions & the time of day" "Everyday Radio Waves - CORRECT ANSWER 1) Bluetooth uses short-wave radio signals to send data over short distances between devices without wires 2) Waves used for TV & FM radio transmissions have very short wavelengths - to get reception, you must be in direct sight of the transmitter" "Microwaves - Satellite Communication - CORRECT ANSWER Used for communication to and from satellites Slight time delay between a signal being sent & received from a satellite due to the long distance it's had to travel" "Satellite TVs - CORRECT ANSWER The signal from a transmitter is transmitted into space where it's picked up by the satellite receiver dish orbiting above the Earth - the satellite then transmits the signal back to Earth in a different direction where it's received by a satellite dish on the ground" "Microwaves - Microwave Ovens - CORRECT ANSWER The microwaves need to be absorbed by the water molecules in food - use a different wavelength to those used in satellite communication The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to the water molecules - causes the water to heat up The water molecules then transfer this energy to the rest of the food molecules by heating - quickly cooks the food" "Infrared Radiation - CORRECT ANSWER Emitted by all hot objects - the hotter the object, the more IR radiation it emits IR cameras are used to detect IR radiation & monitor temperature - the camera detects the radiation & turns it into an electrical signal, displayed on screen as a picture - the hotter an object, the brighter it is Absorbing IR radiation causes objects to get hotter - food can be cooked using IR radiation as the temperature of the food increases when it absorbs it Electrical heaters contain long pieces of wire that emit lots of IR radiation, which is absorbed by objects & the air of the room - the energy from the IR waves is transferred to their thermal energy stores to increase their temperature" "Visible Light Waves - CORRECT ANSWER Optical fibres are thin glass/plastic fibres that can carry data over long distances as pulses of visible light Work because of reflection - the light rays are bounced back and forth until they reach the end of the fibre Light is not easily absorbed or scattered as it travels along a fibre" "Ultraviolet Radiation - CORRECT ANSWER Fluorescent lights generate UV radiation, which is absorbed & re-emitted as visible light by a layer of phosphorus on the inside of the bulb The ink of security pens will glow under UV light, but it's invisible otherwise - helps the police identify your property if it's stolen UV radiation is produced by the Sun & exposure to it gives people a suntan UV lamps at tanning salons are used to give artificial suntans - overexposure can be dangerous" "Properties of fluorescent lights - CORRECT ANSWER 1) They emit light - why they look so bright 2) They're energy-efficient - good to use when light is needed for long periods of time e.g. classrooms" "X-Rays - CORRECT ANSWER Used by radiographers in hospitals to see if a person has any broken bones They pass easily through flesh but not so easily through denser materials e.g. bones & metals The amount of radiation absorbed gives you an X-ray image Used to treat people with cancer (radiotherapy)" "Gamma Rays - CORRECT ANSWER Used to treat cancer - high doses of gamma rays kill all living cells, therefore they are used to destroy the cancer cells Used as a medical tracer - a gamma-emitting source is injected into the patient & its progress is followed around the body Can be harmful, so radiographers wear lead aprons & stand behind a lead screen or leave the room to keep their exposure to a minimum" "Low Frequency Waves - CORRECT ANSWER Don't transfer much energy and mostly pass through soft tissue without being absorbed" "High Frequency Waves - CORRECT ANSWER Transfer lots of energy & so can cause lots of damage, e.g: 1) UV radiation damages surface cells, which can lead to sunburn & cause skin to age prematurely - some more serious effects include blindness & an increased risk of skin cancer 2) Gamma rays & x-rays are types of ionising radiation - can cause gene mutation or cell destruction & cancer" "What is radiation dose? - CORRECT ANSWER A measure of the risk of harm from the body being exposed to radiation The risk depends on the total amount of radiation absorbed & how harmful the type of radiation is Measured in sieverts (Sv) or millisieverts (mSv)" "CT scans - CORRECT ANSWER Uses X-rays & a computer to build up a picture of the inside of a patient's body Head = 2.0mSv Chest = 8.0mSv A CT scan on someone's chest means they are four times more likely to suffer damage to their genes than if they had a head scan" "Convex Lens - CORRECT ANSWER Bulges outwards & causes rays of light parallel to the axis to be brought together (converge) at the principal focus - where the rays hitting the lens parallel to the axis all meet" "Concave Lens - CORRECT ANSWER Caves inwards & causes parallel rays of light to spread out (diverge) The principal focus is the point where rays hitting the lens parallel to the axis appear to all come from - they meet up at a point behind the lens" "What is the focal length? - CORRECT ANSWER The distance from the centre of the lens to the principal focus" "Rules for Refraction - Convex Lens - CORRECT ANSWER 1) An incident ray parallel to the axis refracts through the lens & passes through the principal focus on the other side 2) An incident ray passing through the principal focus refracts through the lens & travels parallel to the axis 3) An incident ray passing through the centre of the lens carries on in the same direction" "Rules for Refraction - ConcavE Lens - CORRECT ANSWER 1) An incident ray parallel to the axis refracts through the lens & travels in line with the principal focus (it appears to have come from the principal focus) 2) An incident ray passing through the lens towards the principal focus refracts through the lens & travels parallel to the axis 3) An incident ray passing through the centre of the lens carries on in the same direction" "What is a real image? - CORRECT ANSWER Where the light from an object comes together to form an image on a 'screen' - like the image formed on the eye's retina" "What is a virtual image? - CORRECT ANSWER When the rays are diverging, so the light from the object appears to be coming from a completely different place" "How do you describe an image? - CORRECT ANSWER 1) How big it is compared to the object 2) Whether it's upright or inverted relative to the object 3) Whether it's real or virtual" "What type of image do concave lenses always produce? - CORRECT ANSWER A virtual image - the image is the right way up, smaller than the object & on the same side of the lens as the object" "Magnifying Glasses - CORRECT ANSWER Use a convex lens The object being magnified must be closer to the lens than the focal length A magnified virtual image is created - the light rays don't actually come from the place where the image appears to be" "Magnification Formula - CORRECT ANSWER Image height = Magnification x Object Height" "What part of the EM spectrum do we see? - CORRECT ANSWER Visible light - a range of wavelengths we perceive as different colours" "Wavelength of violet - CORRECT ANSWER 400nm" "Wavelength of red - CORRECT ANSWER 700nm" "What colours can't you make by mixing? - CORRECT ANSWER Pure red, green and blue" "What happens when all the different colours are put together? - CORRECT ANSWER White light is created" "Opaque objects - CORRECT ANSWER Don't transmit light When visible light hits them, they absorb some wavelengths of light & reflect others Their colour depends on which wavelengths of light are most strongly reflected - the other wavelengths of light are absorbed" "What happens to opaque objects that aren't a primary colour? - CORRECT ANSWER 1) They are reflecting the wavelengths of light corresponding to that colour 2) They are reflecting the wavelengths of the primary colours that can mix together to make that colour" "White objects - CORRECT ANSWER Reflect all of the wavelengths of visible light equally" "Black objects - CORRECT ANSWER Absorb all wavelengths of visible light" "Transparent & Translucent objects - CORRECT ANSWER Transmit light e.g. not all light that hits the surface of the object is absorbed or reflected - some can't pass through Their colour is related to the wavelengths of light transmitted and reflected by it" "What are colour filters? - CORRECT ANSWER They're used to filter out different wavelengths of light so that only certain colours are transmitted - the rest are absorbed Primary colour filters only transmit that colour Filters that aren't for primary colours let through both wavelengths of light for that colour & the primary colours that can be added together to make that colour" "Infrared Radiation - Absorption & Emission - CORRECT ANSWER An object that's hotter than its surroundings emits more IR radiation than it absorbs as it cools down An object that's cooler than its surroundings absorbs more IR radiation than it emits as it warms up An object at a constant temperature emits infrared radiation at the same rate that it absorbs it" "What type of surfaces are better at absorbing & emitting radiation? - CORRECT ANSWER Black is better than white Matt is better than shiny" "What is a Leslie cube? - CORRECT ANSWER A hollow, watertight, metal cube, whose four vertical faces have different surfaces They are used to investigate ER emission by different surfaces" "What is a perfect black body? - CORRECT ANSWER An object that absorbs all of the radiation that hits it - no radiation is reflected or transmitted Best possible emitters of radiation" "What is intensity? - CORRECT ANSWER The power per unit area e.g. how much energy is transferred to a given area in a certain amount of time It increases with temperature It will increase more rapidly for shorter wavelengths" "What do all objects emit? - CORRECT ANSWER Electromagnetic radiation - due to the energy in their thermal energy stores" "What does the overall temperature of the Earth depend upon? - CORRECT ANSWER The amount of radiation it reflects, absorbs and emits" "Will more radiation be absorbed when it's day or night? - CORRECT ANSWER Day - the Sun transfers radiation to the Earth where it is absorbed, thus causing an increase in local temperature" "Global warming - CORRECT ANSWER If the atmosphere starts to absorb more radiation without emitting the same amount, the overall temperature will rise until absorption and emission are equal again" "What causes sound waves? - CORRECT ANSWER Vibrating objects - these vibrations are passed through the surrounding medium as a series of compressions and rarefactions" "Travelling of Sound Waves - CORRECT ANSWER Sound waves travel faster in solids than in liquids, and faster in liquids than in gases When a sound wave travels through a solid, it does so by causing the particles in the solid to vibrate" "Where can't sound travel? - CORRECT ANSWER Space - it's mostly a vacuum, therefore there are no particles to move or vibrate" "Process of sound reaching the ear - CORRECT ANSWER 1) Sound waves that reach your eardrum can cause it to vibrate 2) These vibrations are passed on to tiny bones in your ear called ossicles, through the semicircular canals & to the cochlea 3) The cochlea turns these vibrations into electrical signals which get sent to your brain & allow you to sense the sound" "What range frequency can humans hear? - CORRECT ANSWER Between 20Hz and 20kHz" "What limits human hearing? - CORRECT ANSWER 1) The size of our eardrum 2) The shape of our eardrum 3) The structure of all the parts in the ear that vibrate to transfer the energy from the sound wave" "Sound Waves - Reflection - CORRECT ANSWER Sound waves are reflected by hard, flat surfaces Echoes are just reflected sound waves" "Sound Waves - Refraction - CORRECT ANSWER Sound waves will refract as they enter different media As they enter denser material, they speed up - when a wave travels into a different medium, its wavelength changes and its frequency stays the same, thus causing the change in speed" "The stronger the magnetic field... - CORRECT ANSWER ...The closer together the magnetic field lines are" "Where is the magnetic field strongest? - CORRECT ANSWER At the poles of the magnet - the magnetic forces are always strongest at the poles" "Two of the same poles = - CORRECT ANSWER Repulsion of each other" "Two different poles = - CORRECT ANSWER Attraction to each other" "What do compasses do? - CORRECT ANSWER They show the direction of magnetic fields - they contain a tiny bar magnet whose north pole is attracted to the south pole of any other magnet it is near" "Why do compasses always point north? - CORRECT ANSWER The Earth generates its own magnetic field - magnetosphere Shows the core of the Earth must be magnetic The core is solid iron surrounded by molten iron - movement of molten iron around the core creates the field" "What are the two types of magnet? - CORRECT ANSWER Permanent magnet & induced magnet" "Permanent magnets - CORRECT ANSWER They produce their own magnetic field They are attracted to induced magnets" "Induced magnets - CORRECT ANSWER They are magnetic materials that turn into a magnet when they're put into a magnetic field They're attracted to permanent magnets When you take away the magnetic field, they quickly lose their magnetism and stop producing a magnetic field" "What happens when a current flows through a wire? - CORRECT ANSWER A magnetic field is created around the wire - the field is made up of concentric circles perpendicular to the wire, with the wire in the centre Changing the direction of the current changes the direction of the magnetic field" "The larger the electric current... - CORRECT ANSWER ...The stronger the magnetic field will be" "How do you increase the strength of a magnetic field? - CORRECT ANSWER By wrapping the wire into a coil called a solenoid - the field lines around each loop of wire line up with each other, which results in lots of field lines pointing in the same direction that are very close together" "What happens when you put a block of iron in the centre of a wire coil? - CORRECT ANSWER The iron core becomes an induced magnet whenever the current is flowing, therefore the field strength of the solenoid becomes even stronger - the solenoid becomes an electromagnet" "Uses of Electromagnets - CORRECT ANSWER 1) Cranes - used to attract and pick up things made from magnetic materials e.g. iron, steel - using an electromagnet means the magnet can be switched on when you want to pick stuff up & switched off when you want to drop it 2) Within other circuits to act as switches - when the switch is closed, the electromagnet turns on to attract the iron contact on the rocker, which will pivot & close the contacts, completing circuit two & turning on the motor" "What is the motor effect? - CORRECT ANSWER When a current-carrying wire is put between magnetic poles, the magnetic field around the wire interacts with the magnetic field it has been placed in. This causes the magnet & the conductor to exert a force on each other - this can cause the wire to move" "How do you experience the full force? - CORRECT ANSWER Position the wire at 90° to the magnet - a parallel wire will result in no force at all" "Where does the force always act? - CORRECT ANSWER At right angles to the magnetic field of the magnets & the direction of the current in the wire" "What increases with the strength of the magnetic field? - CORRECT ANSWER The magnitude (strength) of the force, which will also increase with the amount of current passing through the conductor" "Equation for Force - CORRECT ANSWER Force (N) = Magnetic Flux Density (T, tesla) x Current (A) x Length (m) F=BIl" "What does the force acting on a conductor in a magnetic field depend on? - CORRECT ANSWER 1) The magnetic flux density 2) The size of the current through the conductor 3) The length of the conductor that's in the magnetic field" "What is the magnetic flux density? - CORRECT ANSWER A measure of how many field (flux) lines there are in a region - shows the strength of the magnetic field" "Fleming's Left-Hand Rule - CORRECT ANSWER Used to find the direction of a force 1) Use your left hand and point your First Finger in the direction of the Field 2) Point your seCond finger in the direction of the Current 3) Your thuMb will then point in the direction of the force (Motion)" "What does Fleming's Left-Hand Rule show? - CORRECT ANSWER If either the current or the magnetic field is reversed, then the direction of the force will also be reversed" "DC Motors - CORRECT ANSWER Forces act on the two side arms of a coil of wire that's carrying a current - the usual forces which act on any current in a magnetic field Since one coil is on a spindle, it rotates as the forces act one up & one down The split-ring commutator swaps the contacts every half turn to keep the motor rotating in the same direction The direction of the motor can be reversed by swapping the polarity of the dc supply (reversing the current) or swapping the magnetic poles over (reversing the field)" "Electromagnets - Loudspeakers & Headphones - CORRECT ANSWER 1) An alternating current is sent through a coil of wire attached to the base of a paper cone 2) The coil surrounds one pole of a permanent magnet & is surrounded by the other pole, so the current causes a force on the coil 3) When the current reverses, the force acts in the opposite direction, causing the cone to move in the opposite direction too" "How do loudspeakers & headphones create sound waves? - CORRECT ANSWER Variations in the current make the cone vibrate - makes the air around the cone vibrate & create variations in pressure, causing a sound wave The frequency of the sound wave is the same as the frequency of the ac, so by controlling the frequency of the ac, you can alter the sound wave produced" "What is the generator effect? - CORRECT ANSWER The induction of a potential difference (& current if there's a complete circuit) in a wire is moving relative to a magnetic field or experiencing a change in a magnetic field" "How do you create the generator effect? - CORRECT ANSWER Shift a magnet in a coil of wire/a conductor in a magnetic field from side to side - creates a little 'blip' of current if the conductor is part of a complete circuit Moving the magnet/conductor in the opposite direction to reverse the p.d. or reverse the magnet's polarity" "How do you produce an alternating current? - CORRECT ANSWER Keep the magnet/coil moving backwards & forwards to produce a p.d. that keeps swapping direction - an a.c." "What do induced currents do to the charge they made? - CORRECT ANSWER They oppose it - they act against the change that made the magnetic field" "How do you change the size of the induced potential difference? - CORRECT ANSWER Change the rate that the magnetic field is changing 1) Increase the speed of the movement - cutting more magnetic field lines in a given time 2) Increase the strength of the magnetic field - make more field lines that can be cut" "What generates an alternating current? - CORRECT ANSWER An alternator - their construction is similar to a motor" "Generation of an alternating current - CORRECT ANSWER 1) As the coil is spun, a current is induced in the coil - this current changes direction every half-turn 2) Instead of a split-ring commutator, alternators have slip rings & brushes so the contacts don't swap every half turn" "What generates a direct current? - CORRECT ANSWER Dynamos" "Generation of a direct current - CORRECT ANSWER 1) Instead of slip rings, they have a split-ring commutator 2) This swaps the connection every half turn to keep the current flowing in the same direction" "What are oscilloscopes? - CORRECT ANSWER They show how the potential difference generated in the coil changes over time" "Oscilloscopes - alternating current - CORRECT ANSWER This is a line that goes up and down, crossing the horizontal axis" "Oscilloscopes - direct current - CORRECT ANSWER The line isn't straight, but it stays above the horizontal axis as p.d. is always positive" "How do you increase the overall p.d.? - CORRECT ANSWER Increase the frequency of revolutions - this also creates more peaks" "Microphones - CORRECT ANSWER Loudspeakers in reverse 1) Sound waves hit a flexible diaphragm that is attached to a coil of wire, wrapped around a magnet 2) This causes the coil of wire to move in the magnetic field, which generates a current 3) The movement of the coil depends on the properties of the sound wave - louder sounds make the diaphragm move further" "What are transformers made of? - CORRECT ANSWER A primary coil, a secondary coil and an iron core" "What happens when the alternating p.d. is applied across the primary coil of the transformer? - CORRECT ANSWER The iron core magnetises & demagnetises quickly - this changing magnetic field induces an alternating pd in the secondary coil If the secondary coil is part of a complete circuit, a current is induced" "Step-Up Transformers - CORRECT ANSWER Step the potential difference up They have more turns on the secondary coil than the primary coil" "Step-Down Transformers - CORRECT ANSWER Step the potential difference down They have more turns on the primary coil than the secondary coil" "Transformer Equation - CORRECT ANSWER Input potential difference (V) / Output potential difference (V) = Number of turns on primary coil / Number of turns on secondary coil Vp/Vs=np/ns" "Potential difference & Current Equation - CORRECT ANSWER Pd across secondary coil (V) x Current through secondary coil (A) = Pd across primary coil (V) x Current through primary coil (A) VsIs=VpIp" "How does an electric motor use the motor effect of electromagnets to create motion? - CORRECT ANSWER 1) The force on one side of the wire causes it to move up 2) The force on the other side of the wire causes it to move down 3) The motor rotates" "Why are the brushes used to connect the split-ring to the battery made of graphite? - CORRECT ANSWER 1) Graphite is an excellent conductor 2) It causes very little friction on the conducting ring" "What is electromagnetic induction? - CORRECT ANSWER How electricity is created in a wire" "How can the amount of current induced be increased? - CORRECT ANSWER 1) Increase the number of coils 2) Increase the speed at which the magnet/coil moves 3) Increase the strength of the magnet" "What way does the current always travel? - CORRECT ANSWER From positive to negative" "Is the force between a magnet & a magnetic material always attractive or repulsive? - CORRECT ANSWER Always attractive" "What is the magnetic field like inside & outside a solenoid? - CORRECT ANSWER 1) Inside, the field is strong & uniform 2) Outside the coil, the field is just like the one round a bar magnet" "What is the ratio between the primary & secondary potential differences the same as? - CORRECT ANSWER The rate between the number of turns on the primary & secondary coils" "Process of Forming A Star - CORRECT ANSWER 1) Cloud of dust and gas 2) Protostar 3) Main sequence star 4a) Red Giant 5a) White Dwarf 6a) Black Dwarf 4b) Red Super Giant 5b) Supernova 6b) Neutron star 6c) Black hole" "Process of Forming A Star - Stage One - CORRECT ANSWER Stars initially form from a cloud of dust and gas - a nebula" "Process of Forming A Star - Stage Two - CORRECT ANSWER The force of gravity pulls the dust and gas together to form a protostar. The temperature rises as the star gets denser and more particles collide with each other. When the temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei. This gives out huge amounts of energy, which keeps the core of the star hot - a star is born" "Process of Forming A Star - Stage Three - CORRECT ANSWER The star enters a long stable period where the outward pressure caused by the nuclear fusion that tries to expand the star balances the force of gravity, pulling everything inwards. In this stable period, it's called a main sequence star and it typically lasts several billion years The Sun is in the middle of this stable period" "Process of Forming A Star - Stage Four - CORRECT ANSWER Eventually, the hydrogen begins to run out. The star then swells into a red giant (if it's a small sta) or a red super giant (if it's a big star). It becomes red because the surface cools. Fusion of helium (and other elements) occurs. Heavier elements (up to iron) are created in the core of the star" "Process of Forming A Star - Red Giant - Stage Five - CORRECT ANSWER A small-to-medium-sized star like the Sun then becomes unstable and ejects its outer layer of dust and gas. This leaves behind a hot, dense solid core - a white dwarf" "Process of Forming A Star - Red Giant - Stage Six - CORRECT ANSWER As a white dwarf cools down, it emits less and less energy. When it no longer emits a significant amount, it is called a black dwarf" "Process of Forming A Star - Red Super Giant - Stage Five - CORRECT ANSWER Big stars start to glow brightly again as they undergo more fusion and expand and contract several times, forming elements as heavy as iron in various nuclear reactions. Eventually, they'll explode in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars. Stars and their life cycles produce and distribute all naturally occurring elements" "Process of Forming A Star - Red Super Giant - Stage Six - CORRECT ANSWER The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star. If the star is massive enough, it will become a black hole - a super dense point in space that not even light can escape from" "What are planets? - CORRECT ANSWER Large objects that orbit a star There are 8 in our solar system Their gravity is strong enough to have pulled in any nearby objects apart from their natural satellites" "What are dwarf planets? - CORRECT ANSWER Planet-like objects that orbit stars, but don't meet all of the rules for being a planet They're basically too small to be a planet e.g. Pluto" "What are moons? - CORRECT ANSWER They orbit planets They're a type of natural satellite" "What is the Milky Way galaxy? - CORRECT ANSWER A massive collection of billions of stars that are all held together by gravity" "How do planets move around the Sun? - CORRECT ANSWER They travel in almost circular orbits The same happens for the Moon orbiting the Earth" "What force allows planets to constantly accelerate? - CORRECT ANSWER The gravitational force (gravity) between the planet and the Sun or the planet and its satellites" "What does instantaneous velocity do to planets? - CORRECT ANSWER It keeps them travelling in a circle" "The closer to the star/planet... - CORRECT ANSWER ....The stronger the gravitational force is, and the stronger the force, the faster the orbiting object needs to travel to remain in orbit" "How do you create a stable orbit? - CORRECT ANSWER If the speed of the object changes, the size (radius) of its orbit must change as well Faster moving objects will move in a stable orbit with a smaller radius than slower moving ones" "What is red-shift? - CORRECT ANSWER When the wavelengths from distant galaxies shift towards the red end of the spectrum in order to be longer than they should be An increase in wavelength" "What does red-shift suggest? - CORRECT ANSWER The source of light is moving away from us - distant galaxies are receding very quickly" "The greater the red-shift... - CORRECT ANSWER ...The further away the galaxy is - therefore, the galaxies further away are moving away faster than close ones" "What is the Big Bang theory? - CORRECT ANSWER Initially, all the matter in the universe occupied a very small space. This tiny space was very dense, therefore it was very hot. Then, it exploded - space started expanding and the expansion is still going on" "What do scientists currently think the universe is made up of? - CORRECT ANSWER Mostly dark matter and dark energy" "What is dark matter? - CORRECT ANSWER An unknown substance which holds galaxies together, but doesn't emit any electromagnetic radiation" "What is dark energy? - CORRECT ANSWER It's responsible for the accelerated expansion of the universe" "What did scientists discover about the movement of galaxies in 1998? - CORRECT ANSWER The distant galaxies are moving away from us faster and faster - the speed at which they're receding is increasing" "How many planets are in our Solar System? - CORRECT ANSWER 8 planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune and Uranus" "What is the balloon model? - CORRECT ANSWER A balloon covered in pompoms - when you blow into the balloon, it stretches and the pompoms move further away from each other The balloon represents the universe and each pompom is a galaxy - as time goes on, space stretches and expands, moving the galaxies away from each other Simple model - balloons only stretch so far and there would be galaxies inside the balloon too Shows the expansion of space" "What is the force responsible for circular motion? - CORRECT ANSWER Gravity" "Criteria for a planet - CORRECT ANSWER 1) Orbits a star 2) Has sufficient mass to be round or nearly round 3) Not a satellite of another object 4) Has removed debris & small objects from the area around its orbit" "Criteria for a moon - CORRECT ANSWER 1) No lower limit 2) Every natural satellite with an orbit around a planet" "What is a natural satellite? - CORRECT ANSWER A celestial body that makes an orbit around a planet, including the 8 major planets, dwarf planets & minor planets" "What is an artificial satellite? - CORRECT ANSWER Human-built objects orbiting a celestial body" "How do you increase the centripetal force in circular motion? - CORRECT ANSWER 1) Increase the speed of rotation 2) Increase the radius 3) Increase the mass of the object" "What is the Doppler Effect? - CORRECT ANSWER The relative velocity between the source & the observer" "What is Cosmic Microwave Background Radiation? (CMBR) - CORRECT ANSWER Leftover radiation from the start of the universe that has been red-shifted into a microwave radiation It can only be explained by the big bang" "What is the big bang? - CORRECT ANSWER A hot dense state" "What is the Steady State Theory? - CORRECT ANSWER The original theory before the big bang theory As the universe expanded, new matter was created to fill in the empty gaps - kept the density of the universe constant Violates the law of the conservation of mass" ""What is ultrasound? - CORRECT ANSWER Sound waves beyond the range of human hearing - 20,000Hz" "What is partial reflection? - CORRECT ANSWER When a wave passes from one medium to another, some of it is reflected off the boundary between the two media whilst some is transmitted" "Partial reflection of ultrasound waves - CORRECT ANSWER If you point a pulse of ultrasound at an object, wherever there are boundaries between one substance & another, some of the ultrasound gets reflected back" "Ultrasound - Medical Imaging - CORRECT ANSWER Ultrasound waves can pass through the body, but whenever they reach a boundary between two different media (like fluid in the womb & the skin of the foetus), some of the wave is reflected back & detected The exact timing & distribution of these echoes are processed by a computer to produce a video image of the foetus" "Ultrasound - Industrial Imaging - CORRECT ANSWER Ultrasound can be used to find flaws in objects e.g. pipes or materials like wood or metal Ultrasound waves entering a material will usually be reflected by the far side of the material - if there is a flaw e.g. a crack inside the object, the wave will be reflected sooner" "What is echo sounding? - CORRECT ANSWER When high-frequency sound waves are used by boats and submarines to find out the depth of the water they are in or to locate objects in deep water" "What happens when a wave arrives at a boundary? - CORRECT ANSWER 1) It can be completely reflected 2) It can be partially reflected" "Seismic Waves - CORRECT ANSWER An earthquake produces seismic waves, which travel out through the Earth They can be detected all over the surface of the planet using seismometers - seismologists work out the time it takes for the shock waves to reach a seismometer and they note which parts of the Earth don't receive the shock waves at all" "Movement of Seismic Waves - CORRECT ANSWER When seismic waves reach a boundary between different layers of material inside the Earth, some waves will be absorbed & some will be refracted Most of the time, if the waves are refracted, they change speed gradually, resulting in a curved path - but, when properties change suddenly, the wave speed changes abruptly & the path has a kink" "Seismic Waves - P-Waves - CORRECT ANSWER Longitudinal They travel through solids & liquids They travel faster than S-waves" "Seismic Waves - S-Waves - CORRECT ANSWER Transverse They can't travel through liquids or gases Slower than P-waves" "Why do scientists study seismic waves? - CORRECT ANSWER By observing how seismic waves are absorbed & refracted, they are able to work out where the properties of the Earth change dramatically" "Measuring the Speed of Sound - Method - CORRECT ANSWER 1) Set up the oscilloscope so the detected waves at each microphone are shown as separate waves 2) Start with both microphones next to the speaker, then slowly move one away until the next two waves are aligned on the display, but have moved exactly one wavelength apart 3) Measure the distance between the microphones to find one wavelength 4) Find the speed of the sound waves passing through the air - the frequency is whatever you set the signal generator to" "Measuring the Speed of Water Ripples - Method - CORRECT ANSWER 1) Using a signal generator attached to the dipper of a ripple tank, you can create waves at a set frequency 2) Use a strobe light to see wave crests on a screen below the tank 3) Increase