Unit 2B physics

what are possible hazards at home?

-long/ frayed cables -water near sockets -damaged plugs

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How many and what are the wired (and colours) in a 3 core cable?

3 separate wires -brown live -blue neutral -green/ yellow earth

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what does the earth wire do?

protecting the wire and for safety, works together with fuse to prevent fire and shocks, attached to metal casing of plug and carries electricity to earth should something go wrong with live or neutral touch metal case

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How do you know the wiring is right in plug?

-right coloured wire is connected to each pin, firmly screwed in -no bare wires shown inside plug -cable grip tightly fastened over cable outer layer -thicker cable require less resistance, so carry more current

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What are the plug features?

metal parts of copper or brass because their good conductors -case, cable grip ad insulation made of rubber/ plastic because their good insulators and flexible too -keeps electricity flowing where it should

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why are metal cases earthed? what does earthing mean?

-reduce danger of electric shock -earthing means case must be attached to earth wire -an earth conductor can become live

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what does double insulated mean?

if appliance has double insulation and no metal parts showing -anything with double insulation doesn't need earth wire, just live and neutral -cables that carry live and neutral are known as two-core cables

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define nuclear fission

large nucleus splits up into two lighter nuclei and releases 2/3 neutrons + energy

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explain how nuclear fission happens in power station

-nuclear power stations generate electricity using nuclear reactors. in reactor, chain reaction takes place, releases energy as heat. heat used to heat water, makes steam, drives steam turbine, connected to electricity generator

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what two fuels are used to split in nuclear fission?

-uranium 235 and plutonium 239

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what is advantage and problems with nuclear power?

-advantage-fuel is cheap ut power is high due to cost of power plant and final decommisioning -disposal of waste -products after fission are highly radioactive. difficult and expensive to dispose of safely -risks of radiation leaks from plant

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define nuclear fussion

two light nuclei join to create larger nucleus -fusion releases large amount of energy (happens in stars)

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Advantage and problem of nuclear fussion

-advantage: doesn't leave a lot of radioactive waste, lot of hydrogen still to use as fuel -problem: only at high temperatures- about 10000000C, need extremely strong magnetic field

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what is the nebula?

-clouds of dust and gas initially forming

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what is a protostar?

-force of gravity spiralling clouds of dust and gas to form protostar

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what is a main sequence star?

-gravitational energy into heat energy, temp rises -temp high enough, experience nuclear fusion to form helium nuclei and give out heat and light -star is born -enters log stable where heat balances force of gravity -maintain millions of years

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what is process if star is same is size as sun?

-eventually hydrogen runs out, heavy elements e.g iron made. star swells to red giant. red,as surface is cool -becomes unstable, ejects outer layer of dust and gas (planetary nebula) -leaves dense core (white dwarf) -cools to black dwarf & disappear

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what is process if star is bigger than sun?

-big stars, glow brightly, undergo more fusion and expand&contract, forming heavier elements -explode in supernova, forming heavier elements and ejects to universe to form new planets and stars -leaves dense core called neutron star or black hole

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explain the plum pudding model

JJ thomson suggested that atoms were spheres of +ve charge with tiny -ve elctrons stuck in them like plums in a plum pudding

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Who rejected the plum pudding model

Ernest Ruthersford and Marsden

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explain the experiment Ernest Ruthersford and Marsden did?

-firing a beam of alpha particles at thin gold foil -most alpha particles went straight through (most of atom is empty space), some deflected at various points (centre is +ve, repels) -very few came straight back (+ve centre is very dense)

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what did Ernest Ruthersford and Marsden come up with?

- with the nuclear model of the atom -nucleus is tiny, makes up most of the mass of atom, contains protons (+ve) and neutrons (neutral) giving overall +ve charge -rest of atom is empty space -(-ve) electrons go around nucleus, give atom,overall size

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What is radioactivity and what happens in radioactive substances?

-totally random process, cannot say when something decays. radioactive substances give out radiation from nuclei of their atoms -unaffected by physical conditions

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what do radioactive substances spit out?

three types of radiation: -alpha -gamma -beta

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what is background radiation and what sources can it come from?

-a radiation that present all the time, all around us, wherever you go. -sources: air (radon gas), food, rocks, building materials -space (cosmic rays) -man-made sources e.g. nuclear weapons

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what are alpha particles?

- 2 neutrons and 2 protons (same as helium nucleus) -don't penetrate far into materials, stopped quickly -because of size, strongly ionising, meaning they bash into a lot of atoms and knock electrons off them creating lots of electrons

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what are beta particles?

-move quite fast -their electrons -penetrate moderately, long range in air -moderately ionising -for every B particle emitted, one neutron turns to protons -charge of -1

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what are gamma rays?

-penetrate far into materials without stopping and passing straight through air -weakly ionising, pass through rather than colliding -no mass and no charge

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what is static electricity?

-about charges which are not free to move -build up in one place, ends up with spark when they do move -e.g. insulating materials

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how does friction happen in build up of static?

-certain insulating material rubbed together, -ve charged electrons scraped of one and dumped to another -leaves +ve charge on one and -ve charge on other

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what happens in polyethene rod?

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how are the charges affected in movement of electrons?

+ve static charge , caused by electrons moving somewhere else -materials lose -ve charge, left with equal +ve charge

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what charges tell you if two objects repel or attract?

two electrically charged objects, exert force on one another -oppositely electric charges attract +- -same charges repel -- ++ -forces weaker when they are further apart

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what do charges work best on?

-electric charges move easily through material (conductors) e.g. metals

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examples of static electricity?

-jumper -van de graff -baloons

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explain the van de graff generator

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what is current? what is measured and what does this mean?

-rate flow of electric (-ve) charge -when current flows past a poit in circuit for a length of time, then charge passed is given -measured in amps, which 1 coulomb per second -coulomb is a bundle of electrons

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what is voltage? another word for voltage? how to measure it and what does it mean?

-voltage mount of joules per coulomb of charge, it is measured in volts - also known as potential difference - 1 volt is 1 joule of energy per coulomb

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what is resistance? what is units?

ratio of potential difference across a component to the current flowing through it, it is measure in ohms - basically slows the flow down -the greater the resistance across a component, the smaller the current that flows

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how to measure current? give units

current (A) = charge (coulombs) / time (seconds)

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how to work out potential difference?

-P.D (Volts V) = work done (joules) / charge (coulombs) v= i/r

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Name and draw all the circuit symbols?

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How to calculate resistance on circuit?

-find resistance by measuring the current through and potential difference across the component

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what does the Ammeter do?

-measure current (amps) flowing through component -placed anywhere in series, but NEVER IN PARALLEL

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what does the voltmeter do?

-measure PD (volts) across a component -MUST BE IN PARALLEL across component - NOT around variable resistor or battery

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what are the graphs for a resistor filament lamp, and diode? explain the charts

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How does resistance and temperature work?

-when charge flows through resistor, some electrical energy converted to heat energy, resistor gets hot -heat energy causes ions in conductor to vibrate more, current can't flow easily, resistance increases -most resistors

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how to work out potential difference? give units

potential difference (v) = current (a) * resistance (ohms)

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explain what is a diode?

-special device, made from semi conductor material -regulate potential difference in circuits -lets current flow freely through it in one direction, but not other

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what are LEDs? explain

-light emitting diode (LED) emits light when a current flows through it in forward direction -used for lighting -indicates presence of current in circuit -used in appliance e.g. TV when switched on

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What are LDRs? explain

-light dependent resistor -resistor that depends on light -bright light, resistance falls -in darkness, resistance is at highest -e.g. burglar detectors, automatic night lights

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what is thermistor? explain

-temperature dependant resistor -hot conditions, the resistance drops, and cool conditions, the resistance goes up -useful in temp detectors, electronic thermostats

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what are rules applied in series circuits?

-potential difference is shared between various components -current is same everywhere -resistance adds up -cell voltages add up

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what are rules applied in parallel circuits?

-each component is seperately connected to +ve or -ve end of supply, if you remove or disconnect one of them, hardly affect the others -PD is same across all components -current shared between branches apart from voltmeters and ammeters

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how are voltmeters and ammeters different in circuits?

-ammeters always connected in series even in parallel circuit -voltmeters always connected in parallel with a component, even in series circuit

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how does parallel connection in a car work? 2 features

-everything can be turned on and off seperately -everything always gets full voltage from the battery

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What are the two types of supply of electricity called?

-mains supply -battery supply

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what is volts in uk's main supply? what type of supply is it? what is the frequency of this supply?

-230 volts -an AC supply (alternating current) which means the current is constantly changing direction -frequency is 50 cycles per second or 50 Hz (Hertz)

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what types supply direct current?

-cells and batteries supply direct current. means current flowing in same direction

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what does AC and DC mains supply stand for? what do they mean?

-alternating current, which is just current changing direction -direct current, which is current flowing in same direction

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what is a CRO stand for and what does it do?

-cathode ray oscilloscope (CRO) -get trace of AC supply on screen, of how the voltage of supply changes with time. trace goes up and down in regular pattern, sometimes its +ve, or -ve -plug in DC supply, get straight line

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what are the features on a CRO?

-GAIN DIAL controls how many volts each cm division represents on the vertical axis -timebase dial controls how many milliseconds each division represents on horizontal axis -vertical height of AC trace at any point shows input voltage at that point

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how to find time period on a oscilloscope trace?

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what dos earthing and fuse prevent?

-electrical overloads -

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how do the earth wire and fuse in electrical appliances work together?

-if fault develops, in which live wire somehow touches metal case, because case is earthed, too great a current flows in through live wire, through case and out down the earth wire -surge in current melts fuse, when amount of current is greater than

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apart from people, what else fuses and earthing protect?

-protect the circuits and wiring in appliance, before getting fried if there is a current surge

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what should fuses be at home?

-rated near as possible but just higher than normal operating current -larger current, thicker cable needed to carry it, fuse rating for cables usually increases with cable thickness

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define circuit breakers

-electrical safety device to protect circuit from damage, if too much current flows

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what is a type of circuit breaker?

-used instead of a fuse and earth wire, a Residual Current Circuit Breaker (RCCBs)

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what are advantages of circuit breakers and one problem

easily reset by flicking a switch on the device. more convenient than fuses which need to be replaced once melted -however lot more expensive to buy than fuses

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how do circuit breakers work?

-when detect surge in current in a circuit, they break the circuit, by opening a switch

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How do RCCBs work?

-detects difference in current and quickly cuts of power by opening a switch

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what normally happens during a current break in a circuit?

-normally exact current flows through live and neutral wires. if somebody touches live wire, small deadly current flows through them to the earth. means neutral wire carries less current than the live wire

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what are advantages of RCCBs than fuses?

-operate much faster than fuses,break circuit as soon as there is current surge, no need to melt like fuse -even work for small current change, which may not be large enough to melt a fuse, small changes can be fatal, so protec against electrocution

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what ways is energy transferred from cells and other sources?

anything supplies electricity supplies energy -cells, batteries, generators etc all transfer energy to components in circuit

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what happens to resistors when current flows through them?

-electrical energy converted into heat energy -more current that flows, more heat is produced -bigger voltage means more heating, pushes more current through

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how is less energy wasted if appliance is efficient?

-more energy efficient light bulbs transfer more of total electrical energy output to useful energy -cost more, but save money back

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what two things does the total energy transferred by an appliance depend on?

-how long the appliance is on -power rating

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what is the power of an appliance? how to calculate energy transferred?

-energy it uses per second -energy transferred= power rating* time

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what is the formula for working out electrical power?

-power = current* potential difference

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how to work out what fuse an appliance needs?

-work out the current needed

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explain PD, energy and charge

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what does the damage caused by radiation depend on?

-how likely you are to suffer damage if you're expose to nuclear radiation depends on the radiation doese

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what does radiation dose depend on?

-type and amount of radiation you've been exposed to -higher the radiation dose, more risk you are of developing cancer

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what can affect the amount of radiation you have been exposed to?

-location -occupation

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what happens in certain underground rocks?

-e.g. granite, can cause higher levels at surface, especially if they release radioactive radon gas, which tends to get rapped inside people's houses

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what happens in nuclear industry workers and uranium miners?

-expose to 10 times the normal amount of radiation -wear protective clothing and face masks to stop them touching or inhaling radioactive material, and monitor radiation does with special radiation badges and regular check ups

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what happens with radiographers?

-work in hospitals using ionising radiation and have higher level risk of radiation exposure -wear lead aprons and stand behind lead screes to protect them prolonged exposure to radiation

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what happens in high altitudes?

-background radiation increases because of more exposure to cosmic rays, means more commercial pilots have increased risk of getting some types of cancers

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what happens underground?

-radiation does increases because of rocks all around, posing risk to miners

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what are alpha and beta particles deflected by?

-electric and magnetic fields

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how do alpha and beta particles work in electric and magnetic fields?

alpha +ve charge, beta --ve charge. when travelling through fields, the particles will be deflected -deflected in opposite directions due to opposite charge -alpha particles have larger charge than beta p, feel greater force in the fields, deflect

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why does gamma radiation not deflect?

-is an electromagnetic wave (EM) and has no charge, doesn't get deflected by electric or magnetic fiels

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which background sources are included in natural sources and which ones are artifical?

natural: cosmic rays, rocks, living thinks artificial: radioactive waster from nuclear stations, nuclear weapons, medical x-rays

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what do artificial sources count for?

about 15 per cent of the average background radiation dose. Nearly all artificial background radiation comes from medical procedures such as receiving x-rays for x-ray photographs

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how is radiation detected in photographic film?

Photographic film goes darker when it absorbs radiation, just like it does when it absorbs visible light. The more radiation the film absorbs, the darker it is when it is developed.

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what is the geiger muller tube?

detects radiation. Each time it absorbs radiation,transmits electrical pulse to counting machine. This makes clicking sound or displays the count rate. The greater the frequency of clicks, or higher count rate, the more radiation the tube absorbs

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how does each type of radiation penetrate through material?

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how can radiation affect your body cells?

When radiation collides with molecules in living cells it can damage them. If the DNA in the nucleus of a cell is damaged, the cell may become cancerous. The cell then goes out of control, divides rapidly and causes serious health problems.

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how is each radioactive source inside the body?

-Alpha radiation is the most dangerous because it is easily absorbed by cells Beta and gamma radiation are not as dangerous because they are less likely to be absorbed by a cell and will usually just pass right through it

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how is each radioactive source outside the body?

Alpha radiation is not as dangerous because it is unlikely to reach living cells inside the body Beta and gamma radiation are the most dangerous sources because they can penetrate the skin and damage the cells inside

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what is meant by the half life of a radioactive isotope?

- The time it takes for the number of nuclei of the isotope in a sample to halve The time it takes for the count rate from a sample containing the isotope to fall to half its starting level

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how to calculate half life?

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examples of radiation is used?

In smoke detectors For sterilising medical instruments For killing cancer cells For dating rocks and materials such as archaeological finds In chemical tracers to help with medical diagnosis For measuring the thickness of materials in

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how does radiation work in tracers?

Doctors may use radioactive chemicals called tracers for medical imaging. Certain chemicals concentrate in different damaged or diseased parts of the body, and the radiation concentrates with it. Radiation detectors placed outside the body detect the

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how is radiation used to measure the thickness of materials?

adiation is used in industry in detectors that monitor and control the thickness of materials such as paper, plastic and aluminium. The thicker the material, the more radiation is absorbed and the less radiation reaches the detector. It then sends si

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what do radiation badges do?

Radiation badges monitor the radiation dose a worker receives.

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explain nuclear reactions when alpha particle is released?

Alpha decay Two protons and two neutrons are lost from a nucleus when it emits an alpha particle. This means that: The atomic mass number decreases by 4 The atomic number decreases by 2

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explain nuclear reactions when beta particle is released?

n beta decay, a neutron changes into a proton plus an electron. The proton stays in the nucleus. The electron leaves the atom with high energy as a beta particle. The nucleus has one more proton and one less neutron when it emits a beta particle. Thi

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Unit 2B physics

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