physics paper 1 Flashcards

Question

# What energy transfers are happening? 1. Hitting a ball with a bat 2. A car slowing (without breaking) 3. A kettle boiling water | 3 marks

Answer 1

1. kinetic from bat mechanically goes to kinetic energy in the ball (and some to thermal mechanically and due to heating) 2. kinetic is transferred mechanically due to friction then by heating to thermal 3. Energy is transferred electrically from the main then Too thermal energy through heating.

Answer 2

- Lubrication - Whenever something moves, there is at least one friction force acting against it - This transfers energy mechanically to thermal energy store Which dissipates into surroundings by heating? - Lubricants can't be used to reduce the friction. They include liquids like oil, which can easily flow between objects and coat them.

Answer 3

- Insulation - In a building, the lower the thermal conductivity of the walls, the slower the rate of energy transfer though them. - Some houses have cavity walls made up of an inner and outer wall with a air gap in the middle, which reduces the amount of energy transferred by conduction. - Conduction is where hotter. particles vibrate and collide with each other, transferring energy from their kinetic store to other particles which make. them vibrate faster. - The thicker the wall, the slower the rate of energy transfer

Answer 4

- fossil fuels like coal oil and natural gas are reliable and have still enough to meet current demands. - Fossil fuels are cheap to extract and run - However, there are still slowly running out and cause environmental problems like global warming and the greenhouse effect and acid rain due to sulfur dioxide + oil spilages - Nuclear power is costly. to build and safely decommission - However, a nuclear power is clean and Will last much longer than fossil fuels but nuclear waste is very dangerous and difficult to dispose of

Answer 5

- Biofuels - Wind - solar - hydro-electric - tides - These will never run out and dont damage the environment. However, the problem is they are unreliable and dependent on the weather.

Answer 6

- renewable energy made by plants or animal dung - carbon neutral (if you grow at the same rate you burn - fairly reliable as crops dont take too long to grow and it can be done all year round - can be stored for an immediate energy demand - cost is high and use neutrients which would be used for crops made for food - forests are sometimes cleared which destroy habitats

Answer 7

- Turbines have generators inside - when wind rotates the blades They turn a generator producing electricity with no pollution. - Initial costs are high, but running costs are low - Lots of them are needed to produce much power as fossil fuels - Some people think they spoil the view and can be noisy and annoying. - They only work when it's windy, so you can't always supply electricity or respond to high demand.

Answer 8

- solar cells use energy transferred by light to create an electric current - Solar power is often used in remote places where power can't normally get to. - There's no pollution - Initial costs are high but there's no running cost - They mainly are used to generate electricity on a relatively small scale (a home) - Solar power is most suitable for sunny countries but can be used in cloudy countries As you can't make solar power at night or increase production when there is extra demand

Answer 9

- Producing hydroelectricity usually involves flooding a valley by building a big dam - Rainwater is caught and allowed out through turbines making electricity with no pollution - There is a big impact on the environment due to the flooding of the valley and possible loss of habitat - A big advantage is that it can immediately respond to an increase in demand as more water can be let through the turbines to generate more electricity - Initial costs are often high but there is minimum running cost and it's very reliable

Answer 10

- They are big dams built across rivers with turbines in them as the tide comes in it fills the estuaries and the water is then let out through turbines at a controlled speed to generate electricity - There is no pollution but they affect boat access and spoil the view and the alter the habitat for wild life - Tides are pretty reliable but the height of the tide is variable and the barrages don't work when the water is the same level both sides - Initial costs are moderately high but there are no fuel costs and minimal running costs

Answer 11

- Electricity in the uk hugely increased as the population got bigger - As appliances get more efficient the usage of energy slowly decreases - Some of our energy is being produced using fossil fuels and nuclear power but the rest is renewable energies - We use a lot of fossil fuels for cars and gas heating - Renewable energies can be used for those purposes as well like solar water heaters to heat buildings - We are trying to increase our renewable energy resources - Pressure from other countries and the public means that the government have introduced targets for renewable energy resources putting pressure on energy providers so they don't lose their business - hybrid and electric cars

Answer 12

- Building new renewable power plants cost money and smaller energy providers are reluctant in doing this as fossil fuels are much more cost effective - There are arguments where new power plants should go as people don't want to live next to wind farms and it could lead to protests - Some energy resources like wind arent as reliable due to them not being able to increase the power output on demand - This means that they would have to use a combination of different power plants - Research into improving reliability and cost of renewable energy resources takes time and money even with funding it might be years before an improvement is made - Making personal changes might also be quite expensive as hybrid and electric cars are more expensive and things like solar panels are still quite pricey

Answer 13

1. The displacement from the rest position to a crest or trough 2. The length of a full cycle of a wave 3. The lowest part of the wave 4. The highest part of the 5. Number of complete cycles per second 6. The number of seconds it takes to do one cycle 7. The middle line of a wave | page 32

Answer 14

** Transverse:** - all Electromagnetic waves - Vibrations are perpendicular to the direction the wave travels - S-waves - ripples and waves in the water ** Longitudinal:** - Vibrations are parallel to the direction of the wave - P-waves - They squash up and scretch out in areas of compression(high pressure) and rarefactions(low pressure)

Answer 15

1. Attach a signal generator to a speaker so you can generate a sound with a specifc fequency 2. Set up an oscilloscope so the detect waves at each microphone show up as separate waves 3. Start with both microphones next to the speaker then slowly move one away until the two waves are aligned on the display but have move exactly one wave length apart 4. Measure the distance between the microphones to find one wavelength 5. do frequency (is what the signal genorator is set to) x wavelength to find the speed | page 33

Answer 16

1. Using a signal generator attach the dripper of the Ripple tank to create water waves at a set frequency 2. dim the lights and turn on the strobe light to see wave patterns made from shadows of wave crests 3. alter the frequency of strobe light until the pattern freezes 4. this means the frequency of wave and light are equal because the wave will be lit at the same point in their cycle each time 5. the distance between each shadow line is equal to one wave length - the the most accurate value measure 10 wave lengths and find the average 6. do frequency ( set by signal generator) x wavelength to get the speed

Answer 17

1. Set up an experiment where an rod secured in the cente and held up by elastic bands 2. Measure and record the length of the metal rod 3. Get a microphone connected to a computer at one end of the rod and get a hammer on the other 4. Tap the rot with the hammer and write down the peak frequency displayed by the computer 5. Repeat this three times and get an average peak frequency 6. Calculate the speed of this wave by doing frequency x wavelength (which is 2x the length of the rod)

Answer 18

- It can be absorbed by the second material - wave transfers energy to the material often thermal store leading to heating - It can be transmitted - The wave carries on travelling through the new material often refracting - It can be reflected - This is where the weave is sent back in the direction it came from causing echos

Answer 19

1. Draw the boundary between two materials and a normal which is 90 degrees to the boundary 2. Draw the incident ray that meets the normal at the boundary 3. the angle between the Ray and the normal is the angle of incidence 4. Now draw the refracted array on the other side of the boundary(If the second material is more dense the ray bends towards the normal otherwise it bends away 5. The angle between the refracted ray and the normal is the angle of refraction

Answer 20

- size - shape - structure

Answer 21

- particals in solid move back and forth - they hit the next particle in the line ect.

Answer 22

1. sound wave gets to your ear causing it to vibrate 2. these vibrations pass on to tiny bones in your ear called ossicles though the semicircular canal nd to the cochlea 3. which turns vibrations into electrical signalswhich get sent t your brain 4. the brain interprets the signals as sounds of diffrent pitches and volumes 5. which depend on the frequency and intensity (higher frequency - higher pitch 6. human hearing is limited to the size and shape of the eardrum and the structure of the diffrent parts that vibrate

Answer 23

- sound at 20,000Hz - when a wave passes from 1 medium to another some is reflected (partial reflection) - this means you can point a pulse of ultrasound at an object and get some ultra sound back - the time/2 of how long it takes to send the pulse and detect it - is how far away it is

Answer 24

**medical imaging:** 1. ultrasound waves can pass though the body but when they reach a boundary some of the wave is reflected back and detected 2. timings and distribution of echos a processed by a computer to produces a video 3. it is complete safe **industry:** - ultrasound can be used to find flaws in pipes and maturials - ultrasound waves entering a maturial will usually be reflected by the far side - if there is a flaw (like a crack) the wave will be reflected sooner

Answer 25

- Sound with frequencies lower than 20Hz - how some animals communicate - can be produced by natural events (e.g. earthquakes)

Answer 26

- seismic waves (P-wave/S-waves) - they refract out boundarys and curve the path - by observing how they are absorbed and refracted scientists were able to work out where properties of the earth changed - this increase our understanding of the internal structure of the size of earths core

Answer 27

P-waves: - longitudinal - passes though solids and liquids - faster then s-waves S-waves: - transverse - only go though solids - slower then P-waves | page 37

Answer 28

- angle of incidence = angle of relection - normal = perpendicular to the boundary - angle of incidence = incident ray to normal - angle of refection = normal to reflected ray - normal is shown as a dotted line

Answer 29

- wave is reflected back into material - only when wave travels from a more dense towards a less dense material - happens when the angle of incidents (i) is larger then the critical angle - every boundary has its own critical angle - when i is less the critical = most is refracted - some is internaly reflected - when i equals critical = most of the ray goes along surface - when i > critical = no ligh comes out more dense area (total internal reflection | page 38

Answer 30

- specular reflection = waves are reflected in a single direction by a smooth surface - this means you get a clear refection (mirror) - diffuse refection = refected on a rough surface and the waves are reflected in all directions - because the normal is diffrent for each ray | page 38

Answer 31

1. Place a rectangular glass block on a piece of paper and trace around it 2. use a ray box to shine a ray of light at the middle of the block at an angle 3. Trace the incident Ray and the emergent Ray on the other side of the block. then remove it and join up the lines To show the path of the refracted ray 4. Draw the normal at a point where the ray enters the block and use a protractor to measure the angle of incidence (between incident ray and normal) and angle of refraction (between refracted ray and normal) 5. Do the same for where the point emerges from the block 6. Repeat this three times keeping the angle of incidence the same 7. Calculate the average for these angles ## Footnote - Make sure you're in a dim room so you can clearly see the ray - The Ray light must be thin so you can easily trace the middle - To do this cut a thin slit in a light box allowing a thin ray of light out

Answer 32

- you should see that the light bends towards the normal as it enters the block - This is because the block will have a higher density - You should then see the ray of light move away from the normal when it leaves the block ## Footnote All electromagnetic waves retract

Answer 33

- Different objects absorb transmit and reflect different wavelengths - Opaque objects do not transmit light - The colour of an object depends on which wavelength of light are reflected - Colours can also mix so a yellow object might look yellow because it is either reflecting yellow or both red and green light - White objects reflect all wavelengths of visible light equally - Black objects absolve all wavelengths - Transparent and translucent objects transmit light Passing through

Answer 34

- They only let certain colours (wavelengths) transmit and the rest are absorbed - If you put a blue collar philtre in front a white object it will look blue because it only lets the blue wavelength pass through - If a blue filter was put in front of a red object it will appear black because all of the light will be absorbed - Primary colour filters only let through that particular light But none primary colour filters will let through both the wavelengths of light corresponding to that colour

Answer 35

Converging (convex): - Thicker middle - causes parallel rays to come together - The principal focus is where All the parallel lines meet diverging (concave): - caves in words - Causes parallel rays to spread out - The principal focus is where the Rays hitting the lens appears to come from if you trace back and till they meet up

Answer 36

- real - It's formed when light rays actually come together to form an image and it can be captured on a screen - virtual - Is when the light rays from the object appear to be coming from a completely different place to where they actually came from and they don't actually come together

Answer 37

- The more powerful the lens the more strongly it converges (brings together) rays of light so the shorter the focal length - in Converging lenses the power is positive and In diverging lenses the power is negative - To make a more powerful lens we would need to have a stronger curved surface - Some materials are better at focusing light than others meaning a powerful lens can be made thinner by changing the material - Using a material that is better at focusing light means you don't have to make the lens as curved to get the same focal length

Answer 38

1. Go from the top of the object and draw a parallel line to the axis of the lens 2. Draw another ray from the top of the object going right through the middle of the lens 3. From the principal focus on the left side draw a The dotted line (angle of i) to Where the hight of the object and the lens meet 4. Mark where the angle of incidence and the line from the object through the middle, meet 5. This is the top of the virtual image 6. The image is always virtual, the right way up, smaller and on the same side | page 42

Answer 39

1. Draw a parallel line from the top of the object to the lens 2. Draw another ray going from the top of the object to though the middle of the lens 3. The incident ray goes from where the parallel line meets the lens through the focusing point on the right 4. Where the incident ray and the line that goes through the middle meet is where the image forms

Answer 40

- more the 2F = real, inverted and smaller - 2F = real, inverted and same size - F=< O < 2F = real, inverted and bigger - less then F = virtual, upright, bigger and on the same side

Answer 41

- Transverse waves - They all travel at the same speed for a vacuum but different speeds in different materials - They are between 10^-5 and 10^4 metres - They are generated by A variety of changes in atoms and their nuclei giving a range of frequencies - They transfer energy from a source to an absorber - The higher the frequency the more energy it transfers

Answer 42

- radio waves - Transmitted through the body without being absorbed - Microwaves - Can be absorbed causing heating of cells - Infrared - Mostly reflected or absorbed by the skin causing some heating And can cause burns - Visible light - Mostly reflected or absorbed by the skin causing some heating - Ultraviolet - Is absorbed but has a higher frequency so more dangerous. it's a type of ionising radiation and can damaged cells possibly leading to skin cancer or eye conditions - X-rays/gamma - ionising and can cause mutations and damage cells And get deeper into tissues

Answer 43

- The higher the intensity of the wavelength the higher the temperature - If the average power that the object absorbs is more than average power it radiates the object heats up vise versa - An object at a constant temperature radius and absorbs the same average power

Answer 44

- The overall temperature depends on the amount of radiation that is reflected, absorbed and emitted - Radiation is reflected and absorbed by Earths atmosphere clouds and surface - During the day lots of radiation is transferred from the sun (increaing temp) but at night radiation is emitted by the atmosphere causing a decrease in the local temperature

Answer 45

1. Wrap 4 identical test tubes with material that is the same but different colours 2. Boil water in a kettle and fill each test tube with the same volume of water 3. Use a thermometer to measure the temperature of the water every minute 4. Seal the test tubes with bungs between the measurements 5. The temperature will decrease quicker in test tubes surrounded by surfaces that are good emitters of radiation

Answer 46

- Alternating currents made up of oscillating charges can produce Oscillating electric and magnetic feilds (what EM waves are made from) - You can produce radio waves by using an alternating current in an electric circuit - The object which charges oscillate to create radio waves is called a transmitter - Transmitted radio waves Ritchie receiver where 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 electrons to oscillate and if it's part of a complete circuit it will generate a alternating current - This current will have the same frequency as the radio wave

Answer 47

- Longwave radio can be received halfway around the world because they can bend around the curved surface of the Earth Allowing the signal to be received even if it isn't in line of sight of the transmitter - Short-wave radio signals Can be received at long distances because they are reflected by the Earth's atmosphere - This allows radio waves to be great for communication and broadcasting - Bluetooth uses shortwave signals to send data over a short distances without wires - Radio waves for TV and radio stations Have very short wavelengths as you must be in direct sight of the transmitter to get reception

Answer 48

- Communication to and from satellites use EM waves which can pass easily through Earths atmosphere - These can usually be microwaves but sometimes high frequency radio waves - For satellite TV the signal from a transmitter is transmitted into space and received by a receiver dish orbiting above Earth - The satellite transmits the signal back to Earth in a different direction, where it's received by a satellite dish on the ground

Answer 49

- The microwaves are absorbed by the water molecules in the food - Microwaves penetrate through a few centimetres into the food before being absorbed and transfering the energy they are carrying to the water molecules in the food causing the water to heat up - The water molecules then transfer this energy to the rest of the molecules in the food by heating which quickly cooks the food

Answer 50

- Infrared radiation is given out by all hot objects - Infrared cameras can be used to detect infrared radiation and monitor temperature - The camera detects the infrared radiation and turns it into an electrical signal which is displayed on a screen (thermal imaging) - Thermal imaging is used by the police to see its suspects that are trying to escape or hide in the dark - Infrared sensors can be used in security systems to detect a change in infrared radiation, causing an alarmed go off or a security light to turn on - absorbing infrared radiation causes objects to get hotter so food can be cooked using infrared radiation as the temperature of the food increases when it absorbs it - Electric heaters use infrared radiation as they contain a long piece of wire that heats up when a current flows through it. This wire then admits lots of infrared radiation which is absorbed by objects and the air so the energy is transferred into a thermal store increasing the temperature

Answer 51

- It can be used to send files between devices - TV remotes use it - Optical fibres are thin glass or plastic fibres that carry data over long distances as pulses of infrared radiation. They usually use a single wavelength to prevent desperation which could lose some information - They use total internal reflection to send lots of data over a long distance

Answer 52

- Illuminating things - Photographic film reacts to light to form an image -> This is how traditional cameras create photos - Digital cameras contain image sensors which detect visible light and generate an electrical signal which is converted into an image that can be stored

Answer 53

- Fluorescence is a chemical where ultraviolet radiation is absorbed and visible light is emitted - They use ultraviolet to admit visible light and are energy efficient so they are good when light is needed for long periods. - Security pens can be used to mark property and only can be seen under ultraviolet light as it will glow up the ink - bank notes and parasports use a similar technique to detect forgeries - It can also be used to sterilise water as it kills bacteria making it safe to drink

Answer 54

- They affect photographic film the same way like it does meaning you can take X ray photographs (now they are produced electronically) - Radiographers In hospitals take X-ray images to help doctors diagnose broken bones as X-rays are transmitted by flesh but absorbed by denser materials like bones - To produce an image, X-ray radiation is directed through the object or body into a detector plate, the brighter bits of the image are where fewer X rays get through producing a negative image - X rays are also used in airport security scanners to detect hidden objects that can't be detected with metal detectors

Answer 55

- Cameras are used to sterilise medical instruments as they kill microbes - Food can be sterilised in the same way as it keeps food fresh for longer without having to freeze it, cook or preserve it and it's perfectly safe to eat - Some medical imaging techniques such as traces use gamma rays to detect cancer - Gamma radiation is also used in cancer treatments as it targets the cancer cells to kill them, Doctors have to be careful to minimise the damage to healthy cells when treating cancer like this

Answer 56

- In 1897 JJ Thompson discovered that electrons could be removed from atoms so atoms must be made of smaller bits - He suggested the plum pudding model where atoms had a face of positive charge with tiny negative electrons in them - In 1909 Rashford tried firing a beam of alpha particles at a thin gold foil They expected all the particles to pass through however some were deflected back - this meant all the Mass was concentrated in the centre (Nucleus) - He realised most of Atom was mostly empty space with a charged nucleus and tiny electrons around it (The nuclear model) - Bohr tweaked this idea where electrons were in fixed orbits and at set distances called energy levels - he suggested that electrons can only exist in these shells and nowhere in between

Answer 57

- Electrons sit in shells where each energy level is a different distance from nucleus - An inner electron can move up to a higher energy level if it absorbs electromagnetic radiation with the right amount of energy - If it does move up a shell it is said to be excited - The electron will quickly fall back into its original energy level and in doing so it will omit the seamount of energy it absorbed - The part of the en spectrum that is admitted from the atom depends on its energy - Higher energy higher frequency - As you move further out from the nucleus the energy level will get closer (smaller diffrents in amount of energy - This means that the further away you are from the nucleus the at less energy will be edmitted

Answer 58

- Radiation that can knock off electrons form an atom Causing it to become ionised

Answer 59

- Isotapes of an element that tend to decay into other elements and give out radiation as they try to become more stable ( They go through radioactive decay ) - Radioactive substances spit out one or more types of ironizing radiation when they decay

Answer 60

- Alpha radiation is when an alpha particle is admitted from the nucleus - An alpha particle is two neutrons and two protons ( Helium nucleus ) - They don't penetrate very far into materials and are quickly stopped by only a few centimetres in the air and is absorbed by a thin sheet of paper - Due to their size they are strongly ionising

Answer 61

- Beta minus is a fast moving electron released by the nucleus - They have virtually no mass and a relative charge of -1 - they have a range of a few metres and are absorbed by a sheet of aluminium - Beta plus particles is a fast moving positron an antiparticle of an electron - It has the same mass but +1 charge - They have a smaller range because when they hit an electron they destroy each other and produce gamma rays - They both are moderately ionising

Answer 62

- After a nucleus has decayed it goes under nuclear rearrangement which releases energy - Gamma rays or waves of EM radiation released by the nucleus that carry this energy - They penetrate far into materials without being stopped and travel long distances through the air - This means they are weakly ironizing because they tend to pass through rather than collide with atoms - Eventually they hit something and do damage - They can be absorbed by thick sheets of lead or metres of concrete

Answer 63

- The mass number decreases by 4 - the atomic number decreases by two - And it emits a alpha particle | page 52

Answer 64

- It loses and neutron but gains a proton so the mass stays the same - the atomic number increases by one as there is one more proton - A beta minus particle is emitted | page 52

Answer 65

- It loses a proton but gains a neutron so the mass doesn't change - The atomic number decreases by one as it lost a proton - A positron is emitted | page 52

Answer 66

- The mass number of decreases by one as it lost a neutron - The atomic number stays the same - A neutron is emitted | page 52

Answer 67

- Radioactive sources contain radioactive isotopes that give out radiation - Decaying nuclei is a random process - The rate which a source decays is called activity and it's measured in Becuerels (Bq) - 1Bq = One decay per second - It can be measured using a Geiger Miller tube which clicks every time it decays radiation - It can be attached to a counter which displays the number of clicks per second - You can detect radiation using a photographic film - The more radiation is exposed to the darker it becomes

Answer 68

- The average time taken for the number of radioactive nuclei in an isotope to half - The activity never reaches zero - short half-life mean the activity falls quickly because the nuclei is very unstable and rapidly decays Meaning is very dangerous because of the high amount of radiation they edmit but they become safe more quickly - A long half-life means the activity falls more slowly because mostly nuclei doesn't decay for a long time - the source just sits there releasing a small amount of radiation. It is dangerous because nearby areas are exposed to radiation for many years

Answer 69

- It naturally occurs in unstable isotopes which are all around us (The air, some foods, buildings and rocks) - It comes from space known as cosmic rays which are mostly from the sun but luckily the Earth's atmosphere protects us from it - Human activity like nuclear explosions or nuclear waste but this represents a tiny proportion

Answer 70

- Irradiation - Objects near a radioactive source are irradiated by it - This does not make it radioactive - Keeping sources in lead lined boxes standing behind barriers or being in a different room our ways of reducing the effect of a radiation - Medical staff who work with radiation also were photographic film badges to monitor their exposure

Answer 71

- If unwanted radioactive atoms get onto an object it becomes contaminated - These contaminating atoms might then decay releasing radiation which could cause harm - this is very dangerous as it may get inside your body - Once someone has been contaminated they are at risk until the contamination is removed or the reactive atoms have decayed - Gloves and tongues should be in use when handling sources to avoid parties getting stuck in your skin - some workers were protective suits to stop them breathing in particles

Answer 72

- It can enter living cells and ionise atoms and molecules within them leading to tissue damage - Lower dosage tend to cause minor damage without killing the cell but can give a rise to mutant cells which divide uncontrollably (cancer) - Higher dosages tend to kill cells completely causing radiation sickness if a lot of cells all get blattered at once - Outside the body beta and gamma radiation is the most dangerous because they can penetrate the body and get to the organs where Alpha can't get through - Inside the body alpha sources are the most dangerous as they're strongly ionising so they can damage in a very localised area meaning it can contaminate

Answer 73

- the lowest activity of a radioactive source the safer it is to be around - if two sources have the same amount of activity the one with the longer half life will be more dangerous - If the initial activity is lower for the longer half life, it will become more dangerous after a certain period as the activity will fall more slowly - You need to find the right balance between the right level of activity that isn't too dangerous for too long - You also need to be careful planning storage and disposal especially with sources with long half life

Answer 74

- A weak source of alpha radiation is placed in a smoke detector close to two electrodes - The source causes ionisation and a current of charged particals to flow - If there is a fire then smoke will be absorbed by the charged particles using the current to stop sounding an alarm

Answer 75

- Food can be eradicated with high dosages of gamma rays which kill all microbes meaning they dont go as bad as quickly - Medical equipment can be sterilised using gamma rays instead of being boiled - irradiation is a particularly good method to sterilise because unlike boiling it doesn't involve high temperatures so things can be sterilised without being damaged - The radioactive source used for this need to be very strong emitter of gamma rays with a reasonably long half life so it don't have to be replaced too often

Answer 76

- A medical tracer is injected into a patient and is moved around the body followed by an external detector this method can be used to detect and diagnose medical conditions e.g. cancer - All isotopes which are taken into the body must be beta or gamma emitters so radiation can pass out of the body without doing too much damage - They should only last a few hours so the radioactivity inside the patient quickly disappears

Answer 77

- Gamma emitting traces are also used in industry to detect leaks in underground pipes - Beta radiation issues in thickness control - This is done by directing radiation through stuff being made (e.g. paper) and putting a detector on the other side and connecting it to a control unit - When the amount of detected radiation changes it means the paper coming out is too thick or too thin so the control unit adjusts the roller to give the correct thickness - It needs to be a beta source because then the paper will partially block the radiation

Answer 78

- positron emission tomography is a technique to show tissue or organ function and can be used to diagnose medical condition - The patient is injected with a substance used by the body contending a positron emitting radioactive isotope with a short half-life acting as a tracer - Positron's Emitted by the isotope meat electrons in the organ and annihilate emitting high energy gamma rays in opposite direction that are detected by detectors around the body - By looking where all the rays meet the tumour can be accurately found - The distribution of radioactivity matches up with the metabolic activity because more of the radioactive thing that was injected is taken up by the cells that are doing work - the isotope used in PET scanning have short half life so it's important they are made close to wherever they're going to be used - Otherwise if it had to be transported over a large difference the activity will be too low the time it arrived at the hospital

Answer 79

internal: - With internal radiation therapy A radioactive material is placed inside the body into or near a tumour through injecting or implanting a small amount of radioactive substance - Alpha emitters are usually injected into the tumour as its strongly ionising and can do a lot of damage put the damage to normal tissue surrounding the tumour is limited because they have such a short range - Beta emitters are often implanted into the tumour before damaging nearby cancerous cells, as they have longer ranges they can damage healthy cells further away - The half life of the source used for internal treatment is usually short to limit the time that radioactive substances are inside the patient's body external: - tumours can be treated externally using gamma rays aimed at the tumour - The radiation is carefully focused on the tumour and sometimes shielding is placed on other areas of the body but some damage can still be done to surrounding healthy cells - The sources in external radiotherapy treatments should have long half lifes so they don't have to be replaced often - The machines used for radiotherapy are often surrounded by feuding and captain-designated rooms to reduce the risk of staff and patience

Answer 80

- A slow moving neutron is fired at a large unstable nucleus - often uranium 235 - the neutron is absorbed by the nucleus making it more unstable causing it to split - When uranium two three five splits it forms two new lighter elements and energy is released - There are lots of different pairs of atoms that uranium can split into but these new nuclei are radioactive - Each time uranium atom splits it also splits out two or three neutrons that can hit other uranium nuclei causing them to split causing a chain reaction

Answer 81

- Neutrons released by fission have lots of energy - These neutrons will only cause other nuclear fission if they are moving slowly enough to be captured by uranium nuclei in the control rods - These slow moving neutrons are called thermal neutrons - To do this the uranium fuel rods are placed in a moderator to slow down the fast moving neutrons - Control rods are often made of boron to limit the rate of fission by absorbing the access neutrons they are placed but in between the few rods and are raised and lowered into the reactor to control the chain reaction - This creates a steady rate nuclear fission where one new neutron produces another fission - If this chain reaction in a nuclear reactor is left to continue unchecked large amounts of energy are released in a very short time causing a runaway reaction which could lead to an explosion

Answer 82

- Energy released by fission is transferred into the thermal energy store of a moderator - This is then transferred to the thermal energy store of the coolant and then the thermal energy store of the cold water passing through the boiler - This causes the water to boil and to the energy to be transferred to the kinetic energy store of the steam - This energy is then transferred to the kinetic energy store of the turbines and then kinetic energy store of the generator - Energy is then transferred away from the generator electrically | page 57 for pic

Answer 83

- Two light nuclei collide at high speeds to join to create a larger heavier nucleus e.g. Hydrogen nuclei confuse to produce a helium nucleus - This heavier nucleus does not have as much mass as two separate light nuclei did - Some of the mass of the lighter nuclei is converted into energy and released

Answer 84

- Fusion has to happen at a very high pressure and 10 million degrees Celsius - Because the positively charged nuclei have to get very close to fuse so the strong forces due to electrostatic repulsion has to be overcome - It's really hard to create the right conditions for fusion as no material can withstand that kind of temperature as it would vaporise so they're hard to make and expenses to try and build - There have been a few experiments but it takes more power than is generated to get the temperature

Answer 85

- - People view it as very negative as they think it's very dangerous - Some people worry that nuclear waste can never be disposed safely as they have long half lives meaning they'll be radioactive for hundreds/thousands/millions of years - There is always a danger that it could leak out and pollute the land, rivers and oceans - Nuclear power also carries the risk of leaks directly from the power station or a major catastrophic like Chernobyl - The overall cost is high due to the initial cost of the power plant and dismantling the nuclear power plant safely takes decades + - Generally they are pretty safe at generating electricity and not as risky as some may think - it is very reliable as it reduces the need for fossil fuels - It does not contribute to global warming so it's much better than fossil fuels - Huge amounts of energy can be generated with a relatively small amount of nuclear material

Answer 86

- Asteroids are lump of rock and metal that orbit the sun, usually found in the asteroid belt - Comets are a lump of ice and dust that orbit the sun and are highly elliptical. some travel near to the sun to the outskirts of our solar your system

Answer 87

- Planets move around the sun in almost circular orbits meaning that it orbits at a constant speed and is constantly accelerating - The force causing this is the centripetal force - This force would cause the object to just fall towards whatever its orbiting but the object is already moving so it just causes it to change direction - The object keeps accelerating towards what is orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps travelling in a circle - The force that makes this happen is provided by the gravitational force between the planet and the sun

Answer 88

- Gravitational field strength depends on the mass - Gravitational filled strength also varied with distance, the closer you are the stronger the force - The stronger the force the larger the instantaneous velocity needed to balance it - So the closer to a star the planet is the faster it has to move to remain in order - For an object in a stable orbit if the speed of the object changes the size of its orbit must do so as well

Answer 89

- **Geocentric** model was the first by the ancient greeks - it stated that everything orbited the Earth in perfect circles - This was because they didn't have telescopes and saw the sun and moon travelling across the sky in the same way every day and light - The next was the **heliocentric** model - it said that the earth and all the other planets orbited the sun in perfect circles - Galileo found the best piece of evidence for this theory as the moons around Jupiter while looking for a telescope He noticed that some stars were in line near the planet But they never moved away showing not everything was orbiting around the Earth - As more technological advancements the evidence for this model increased - The current model still says planets orbit the sun but in an elliptical orbit rather than circular

Answer 90

- The universe has always existed and always exists - As the universe expands new matter is constantly being created - Density stays the same - This new beginning or no end - Supported by red shift

Answer 91

- What was the matter of the universe occupied a very small space - This tiny space was very dense and very hot - Then excluded and space started expanding - This theory gives a finite age for the universe - It's supported by cosmic microwave background radiation and red shift

Answer 92

- Different elements absorb different frequencies of light - Each element produces a Spacific pattern of dark lines at the frequencies that it absorbs in the visible part of the EM spectrum - When we look at light from distant galaxies we see the same patterns but slightly lower frequencies - There's an observed increase in wavelength of light coming from the galaxies and a pattern has been shifted towards the red end of the spectrum (red-shift) - Measurements of the redshifts suggest all the distant galaxies are moving away from us very quickly from all directions - More distant galaxies have a greater red shift meaning they have they are moving away faster providing evidence that the whole universe is expanding | This can have the same effect as the sound from a racing car ## Footnote The noise sounds lower pitch when it's travelling away from you because it drops in frequency (doppler effect)

Answer 93

- Scientists have detected low frequency electromagnetic radiation coming from all parts of the universe - This radiation is mainly the microwave part of the EM spectrum

Answer 94

1. It initially starts from a cloud of dust and gas called a nebula 2. The force of gravity pours the dust and gas together to form a protostar 3. The temperature rises as the star gets denser and more particles collide 4. When the temperature gets high enough hydrogen nuclei undergo nuclear fusion to form helium nuclei giving out a huge amount of energy keeping the core hot 5. A star is born and enters a long stable period 6. During this time the outward pressure caused by thermal expansion balances the force of gravity pulling everything inwards (the heavier the star the shorter is time on the main sequence)

Answer 95

1. Eventually the hydrogen in the core begins to run out and the force due to gravity is larger than the pressure of thermal expansion 2. The store is compressed into its dense and hot enough that hydrogen in its outer layer and helium in its core can undergo fusion 3. This increases the pressure of thermal expansion again making the outdoor layer of the star expand becoming a red giant or a red supergiant if it's a super large star (red due to the cool surface) 4. A small star becomes unstable and ejects its outer layer of dust and gas leaving behind a hot dense solid core Which is a white dwarf

Answer 96

1. They start to glow brightly again as they undergo more fusion to make heavier elements 2. They expand and contract several times as the balance shifts between gravity and thermal expansion 3. Eventually they explode in a supernova 4. the exploding supernova throws the outer layer of dust and gas into space leaving a very dense core called a neutron start 5. If the star is massive enough it will collapse and become a black hole

Answer 97

- They use refraction and reflection to allow you to see the distant objects - Optical telescopes are the ones that detect visible light - You can improve the quality by increasing the aperture of the telescope which is the diameter of the objective lens - Use a higher quality objective lens

Answer 98

- The atmosphere absorbs a lot of light coming from space before it reaches us so to observe the frequencies which are absorbed, you have to be above the atmosphere - Light pollution makes it harder to pick out dim objects and reflects and absorbs light coming from space ## Footnote To get your best view on Earth you should be on the top of a mountain in a dark place

Answer 99

- Optical telescopes are used to look at objects close by and in other galaxies but many objects in the universe aren't detectable using visible light - The telescopes developed for all parts of the EM spectrum allow us to see parts of the universe that we couldn't see before like its structure - X-ray telescopes are a good way to see high temperature events in space like exploding stars - Radio telescopes are responsible for the discovery of cosmic back microwave background radiation helping scientists learn more about the origins of the universe - Bigger telescopes give us a better resolution and can give them more light so we can see things which we couldn't see before it will server improved magnification so we can look further into space and discover new galaxies - Modern telescopes work alongside computers to help create clearer and sharper images