Presentation on theme: "OCR Additional Science"— Presentation transcript:
1 OCR Additional Science 11/04/2017OCR Additional ScienceP4 Radiation for LifeAGAC
2 Equations for this unit (Foundation) 11/04/2017Equations for this unit (Foundation)unit 5unit6
3 the equations needed for this 11/04/2017unit 5This slide showsthe equations needed for thisUnit (Higher)unit6
4 Static Electricity + + - - + - + + + - - - + + - + - - 11/04/2017Static electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used:Rod becomesnegativelychargedRod becomespositivelycharged++--+-+++---++-+--It is only the negative charges-the electrons which move
9 Use of static - Photocopiers 11/04/2017P+1)Photocopiers use static electricity. They work by: 1) Copying an ______ of the page onto a ______ plate, 2) Light then causes the charge to ____ away, leaving an “electrostatic impression” of the page, 3) The charges left on the plate ______ small drops of black powder, 4) The powder is transferred from the plate onto the _____, 5) The paper is _____ to “fix” the powder.imagechargedleakP+2)attract3+4)P+paperheatedWords – heated, leak, paper, image, charged, attract
11 Uses and dangers of Static Electricity 11/04/2017Find out how static electricity is used in the following:1) Laser printers2) Paint sprayer3) DefibrillatorsFind out how static electricity is dangerous in the following situations:1) Fuel pipes2) Hospitals
12 H 11/04/2017 These need to be opposites positive/negative negative/positiveattractedknocked
14 Wiring a plug 1. Earth wire 4. Live wire 5. Fuse 2. Neutral wire 6. 11/04/2018.104.22.168.5.6.Earth wireLive wireFuseNeutral wireCable gripInsulationThe neutral wire of a plug stays at a potential close to zero relative to the EarthThe live wire of a plug alternates between positive and negative potential relative to the Earth
15 Words – large, harm, safety, melt, live, circuit, fuse Fuses11/04/2017Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____.safetylivelargefusemeltcircuitharmWords – large, harm, safety, melt, live, circuit, fuse
16 Words – fuse, fault, metal, surges, touch Earth wires11/04/2017Earth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows.metalfaulttouchsurgesfuseWords – fuse, fault, metal, surges, touch
17 Circuit breakers11/04/2017Residual Current Circuit Breakers (RCCBs) are often used with fuses. They have some advantages over fuses:They are safer – they don’t get hotThey react more quicklyThey can be switched off for repairsThey are easy to resetEach RCCB is attached to a certain circuit, so if one switches off you can see which circuit has a fault
18 Resistance V R I Resistance = Voltage (in V) (in ) Current (in A) Georg Simon Ohm11/04/2017Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me.The resistance of a component can be calculated using Ohm’s Law:VRIResistance = Voltage (in V)(in ) Current (in A)
19 An example question: Ammeter reads 2A A V 11/04/2017Ammeter reads 2AVAWhat is the resistance across this bulb?Assuming all the bulbs are the same what is the total resistance in this circuit?Voltmeter reads 10V
20 What is the resistance of these bulbs? More examples…11/04/20173A6V12V4V2A1A2V3AWhat is the resistance of these bulbs?
21 Resistance Resistance is anything that opposes an electric current. 11/04/2017Resistance is anything that opposes an electric current.Resistance (Ohms, ) = Potential Difference (volts, V)Current (amps, A)What is the resistance of the following:A bulb with a voltage of 3V and a current of 1A.A resistor with a voltage of 12V and a current of 3AA diode with a voltage of 240V and a current of 40AA thermistor with a current of 0.5A and a voltage of 10V
24 Waves- Some definitions… 11/04/20171) Amplitude – this is “how high” the wave is:2) Wavelength () – this is the distance between two corresponding points on the wave and is measured in metres:3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz)
25 Some definitions…11/04/2017Transverse waves are when the displacement is at right angles to the direction of the wave…Just pick out one particle and follow its motionLongitudinal waves are when the displacement is parallel to the direction of the wave…Just pick out one particle and follow its motion
26 Words – depth, reflected, picture, medium Ultrasound11/04/2017Ultrasound is the region of sound above 20,000Hz – it can’t be heard by humans. It can be used in pre-natal scanning:How does it work?Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object.reflectedmediumdepthpictureWords – depth, reflected, picture, medium
27 Other uses of ultrasound 11/04/20171) Echo soundingThe ultrasound is reflected from the sea floor.2) Breaking down kidney stonesUltrasonic waves break kidney stones into much smaller pieces3) Cleaning (including teeth)Ultrasound causes dirt to vibrate dirt off without damaging the object
28 F 11/04/2017 scans to monitor pregnancy break down kidney stones by vibrating particlesmeasure blood flowby measuring frequency changecleaning instrumentsmakes dirt particles shake offtreat cancerusing an intense beam aimed at tumour
30 The structure of the atom 11/04/2017ELECTRON – negative, mass nearly nothingPROTON – positive, same mass as neutron (“1”)NEUTRON – neutral, same mass as proton (“1”)
31 The structure of the atom 11/04/2017ParticleRelative MassRelative ChargeProton1+1NeutronElectron-1MASS NUMBER = number of protons + number of neutronsHe24SYMBOLPROTON NUMBER = number of protons (obviously)
32 Introduction to Radioactivity 11/04/2017Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation:RadiationThe nucleus is more stable after emitting some radiation – this is called “radioactice decay” and the activity is measured in “Becquerels (Bq)”.
33 Types of radiation11/04/20171) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom)neutronsUnstable nucleusNew nucleusAlpha particlehelium2) Beta () – an atom decays into a new atom by changing a neutron into a _______ and electron. The fast moving, high energy electron is called a _____ particle.protonbetaBeta particleNew nucleusUnstable nucleus3) Gamma – after or decay surplus ______ is sometimes emitted. This is called gamma radiation and has a very high ______ with short wavelength. The atom is not changed.energyfrequencyWords – frequency, proton, energy, neutrons, helium, betaUnstable nucleusNew nucleusGamma radiation
34 Changes in Mass and Proton Number 11/04/2017Alpha decay:Am24195Npα42+23793Beta decay:Sr9038Yβ-1+9039
35 Uses of radioactivity 1 Sterilising medical instruments 11/04/2017Sterilising medical instrumentsGamma rays can be used to kill and sterilise germs without the need for heating.
36 Uses of radioactivity 2 Beta detector Rollers Paper Beta emitter 11/04/2017Beta detectorRollersPaperBeta emitterThis is used to make sure the paper/steel is the correct thickness.The pressure on the rollers is adjusted dependingon how much of the beta is received by the detector
37 Uses of radioactivity 3 Smoke detectors Alpha emitter +ve electrode 11/04/2017Smoke detectorsAlpha emitter+ve electrode-ve electrodeAlarmIonised air particlesIf smoke enters here a current no longer flowsThis sets off an alarmThis involves `a NOT gateSee Unit 6
38 Uses of Radioactivity 4 - Treating Cancer 11/04/2017High energy gamma radiation can be used to kill cancerous cells. However, care must be taken in order to enure that the gamma radiation does not affect normal tissue as well.Radioactive iodine can be used to treat thyroid cancer. Iodine is needed by the thyroid so it naturally collects there. Radioactive iodine will then give out beta radiation and kill cancerous cells.
41 H 11/04/2017 all of tumour receives the full dose focussed/directed at/concentratedall of tumour receives the full doseHealthy tissue does notreceive the full dose
42 H 11/04/2017 so gamma can reach the surface low count rate after the blockage
43 Half life11/04/2017The decay of radioisotopes can be used to measure the material’s age. The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay…= radioisotope= new atom formedAfter 2 half lives another half have decayed (12 altogether)After 3 half lives another 2 have decayed (14 altogether)After 1 half life half have decayed (that’s 8)At start there are 16 radioisotopes
45 Dating materials using half-lives 11/04/2017Question: Uranium decays into lead. The half life of uranium is 4,000,000,000 years. A sample of radioactive rock contains 7 times as much lead as it does uranium. Calculate the age of the sample.Answer: The sample was originally completely uranium…1 half life later…1 half life later…1 half life later…8482818…of the sample was uraniumNow only 4/8 of the uranium remains – the other 4/8 is leadNow only 2/8 of uranium remains – the other 6/8 is leadNow only 1/8 of uranium remains – the other 7/8 is leadSo it must have taken 3 half lives for the sample to decay until only 1/8 remained (which means that there is 7 times as much lead). Each half life is 4,000,000,000 years so the sample is 12,000,000,000 years old.
46 An exam question…11/04/2017Potassium decays into argon. The half life of potassium is 1.3 billion years. A sample of rock from Mars is found to contain three argon atoms for every atom of potassium. How old is the rock?(3 marks)The rock must be 2 half lives old – 2.6 billion years
47 Background Radiation 13% are man-made Radon gas Food Cosmic rays 11/04/201713% are man-madeRadon gasFoodCosmic raysGamma raysMedicalNuclear power
48 Uses of radioisotopes - tracers 11/04/2017A tracer is a small amount of radioactive material used to detect things, e.g. a leak in a pipe:If there is ablockage weknow where it isbecause there willbe no gammareading beyond itGamma sourceThe radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected.Tracers can also be used to develop better plant fertilisers and in medicine to detect tumours:
49 Nuclear power stations 11/04/2017These work by using nuclear fission reactions using uranium:Nuclear fuel (uranium) is used to boil water in a “heat exchanger”. The steam drives a turbine.