P1

the whole of p1 flash cards made using/from the ocr revision book

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What is heat a measure of?
Energy
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What happens when a substance is heated?
Its particles gain kinetic energy(KE)--> thus giving them more energy. More Energy = faster movement of the particles in a as or liquid and faster vibrations in a solid.
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How is energy measured?
on an absolute scale.(this means that it can not go lower than 0- as there is a limit to how fast particles can move. Energy is measured in joules(J).
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What is temperature a measure of?
Hotness-- The average kinetic energy of particles in a substance.
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What happens when a substance is heated?
Its temperature and the kinetic energy of its particles increases.The hotter something is the higher its temperature and KE.
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How is tempurature measured?
In degrees celsius. however there are other tempurature scales such as fahrenheit. theses are not absolute scales as the can go below 0.
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How does energy flow from objects?
from hotter to cooler. e.g. warm radiators heat the cold air in the room.
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What happenes if there is a difference in temperature between 2 places?
Energy will flow between them.
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If the temperature is greater what happens to the rate of cooling?
it increases(becomes faster). a hot cup of tea will cool more quickly in a cooler room.
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What is specific heat capacity?
The amount of heat an substamce can store. The amount of energy it takes to raise 1kg of substance by 1 degrees celsius.
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Materials which need to gain lots of energy to warm up (store lots of heat) - release what when they call down?
Lots of energy.
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What is the heat capacity of water?
4200J/kg/degrees celcius.
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Why is water so good for central heating systems?
Its specfic heat capacity is high, once water is heated it stores alot of energy.
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What is the equation for working out the specific heat capacity of a substance?
Energy=Mass X Specific Heat Capacity X Temperature Change
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How much energy is needed to heat 2kg of water from 10 degrees celsius to 100?
energy needed = 2 X 4200(because it is water) X 90 (difference between 100 and 10 degrees) = 756 000J
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What happens to the temperatue of a substance when the intermolecular bonds are being madeand broken?
The temperature stops rising and stabalises.
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Why does temperature stay the same when bonds are breaking?
As the energy (which would increase the temp) is used to break the bonds between substances.
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How is energy used to break intermolecular bonds?
The energy makes the particles with in the substance vibrate/move faster.
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What happens when a substance is condensing or freezing?
Bonds are forming between particles.
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What happens when bonds are formed?
Energy is released.
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When does the temperature begin to go down again, after bonds are formed?
Not until the change in state has taken place. E.g. freezing, condensing, and solidfying.
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How is forming and breaking of bonds shown on a graph?
By straight/ flat lines.
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What is specific latent heat?
Heat/ energy needed to change state e.g. melting.
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What is the specific latent heat of melting?
Engergy needed to boil one kilogram of material without changing it's temperature. The materials have to be at melting temperature already)
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What is the specific latent heat of boiling?
Engergy needed to boil one kilogram of material without changing it's temperature. The materials have to be at boiling temperature already)
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What is the formula specific latent heat?
Energy = maths X specific latent heat
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The specific latent heat of water (for melting) is 334 000 J/Kg. How much energy is needed to melt an ice cube of mass 7g at 0 degrees?
Energy = 0.007 X 334 000 J = 2338J
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Where/ in what does conduction occur?
In solids.
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How is heat passed on by conduction?
In a solid particles are held tightly together. When one particle vibrates it bumps into another and quickly the vibrations are passed on. Faster vibrating particles pass their kinetic energy (heat) to neighbouring particles to vibrate faster.
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Sum up conduction.
The process where vibrating particles pass on extra kinetic energy to neighbouring particules.
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Metals conduct heat really well...Why is this?
Because some of their electrons are free to move inside the metal. Heating makes the electrons move faster and collide with other free electrons, transfering energy. The free electrons will move faster.
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So What does this mean for conduction of none metals?
They have no free electrons - so warm up slowly making good insulation. Thats why metal is good for making saucepans and non metals for the handles.
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What about conduction in liquids and gases?
They conduct heat more slowly than solids - the particles are not held so tightly together, which prevents them bumping into each other so often. Therefore air is a good insulator.
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Where does convection occur?
Convection occurs when the more energetic particles move from the hotter region to the cooler region - taking their heat energy with them.
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Explain convection in liquids and gases?
Heating up a liquid or gas makes particles move faster. The fluid expands becoming less dense and rises above it's cooler denser surroundings (like a hot air balloon) The cooler air takes the place of warm air, this process continues as a circulation
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How do immersion heaters and radiators work?
By convection. The warm air circulates around the room.
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Why can't convection take place in solids?
Because the particles cannot move and just vibrate on the spot.
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How can we reduce convection?
Stop the fluid moving. Clothes, blankets and cavity wall foam insulation all work by trapping pockets of air - so the heat has to conduct very slowly through the pockets of air as well as the material inbetween.
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How do we get heat from the sun?
Radiation.
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How is heat tranferred by radiation?
As infrared waves - these are electrode magnectic, travel in straight lines at the speed of light.
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How is radiation different from conduction and convection (3 ways)?
1) No medium (material) to travel through - occurs in vacuum e.g. space.How heat reaches us from the sun. 2)Only occurs through transparent substances, air, glass, or water 3)Radiation emmited/absorbed by object depends surface colour and texture.
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What are objects continually emitting and absorbing?
Heat radiation.
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Finish the sentences.....the hotter objects get the ____ radiation they _____. Cooler objects will____the heat radiation emitted by hotter things so their temperature ___.
The hotter an object gets, the more heat radiation it emits. Cooler objects will absorb the heat radiation emitted by other hotter things, so the temperature increases.
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Absorbtion and emission rates can depend on surface colour and texture. Explain this with matt black surfaces and light coloured smooth.
Matt black surfaces - good radiation absorbers & emitters. Black radiators help emit heat radiation, a shiny white fridge reflects it. Light coloured, smooth & shiny objects- poor absorbers & emitters Shiney foil behind radiator reflects radiation.
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State an item that is matt black to absorb as much heat as possible?
Solar panels - for heating water.
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State an item that is smooth, shiny and light, to reflect heat away.
A patio heater.
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What is heat radiation important for?
Cooking.
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How do grills and toasters heat food by infrared (heat) radiation?
Heat radiated by a grill is absorbed by particules at the surface of the food - increasing their kinetic energy. This is then conducted or convected to more central parts.
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How can we make grilling food more even?
By lining a grill pan with shiney food, heat radiation is reflected back onto the bottom of the food being grilled. Resulting in it being more evenly cooked.
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How do microwaves use radiation to cook food?
Microwaves are electromagnetic (waves that have a different wave length to infared. Microwaves penetrate 1cm into the layer of food & are asorbed by water or fat molecules - increasing kinetic energy, energy is conducted or convected to other parts.
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Why don't you cover food with foil in the microwave?
The microwaves will be reflected away, so they will not cook the food & it can cause dangerous sparks within the oven.
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What is it okay to cover the food with in the microwave oven and why?
Glass or plastic, as microwaves can pass through it - therefore cooking the food.
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What does insulating your house save?
Money and energy
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What happens to energy in the home?
It is emitted and tranferred (wasted) in different areas.
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What is the name given to things that emit energy?
Sources e.g. radiators
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What is the name given to things that waste, transfer or lose energy?
Sinks e.g windows and computors.
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How can you save energy within your home?
You can insulate your house, so the sinks drain less energy e.g. curtains. Also you can make sources and sinks more efficient so they waste less energy e.g. energy saving light bulbs.
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What is the negative and positive factor of insulation?
It costs money to buy and install insulation or more efficient appliances, but it also saves you money because your energy bills are lower.
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What is the name given to getting back the money you spent on energy bills and the initial cost (equaling)?
pay back time.
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State types of saving energy?
Loft insulation, cavity walls and insulation, draft proofing, thick curtains, double glazing and hot water tank jacket.
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How can we work out pay back time?
It is when you have regained your intial cost and then start benefiting from saving money.
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What are thermograms?
A picture taken with a thermal imaging camera, showing where your house is leaking heat
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What do objects at different temperatures emit?
Infrared rays of diffferent wavelengths. These are shown as different colours, the hotter parts show up as white, yellow and red. Whilst the colder parts are black, dark blue and purple. If a house looks hot it is losing heat.
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Why are useful machines only useful?
Because they convert energy from one form to another. E.G. cars for instance - you put in chemical energy (petrol or diesel) and the engine converts it into kinetic (movement) energy.
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What is the total energy output the same as?
The energy input, but only some of the output energy is useful e.g. every jewel of chemical energy put into your car your only get a fraction of it converted into useful kinetic energy.
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Why do you only get a fraction of energy from the energy input?
Because input energy is always lost or wasted often as heat e.g. in a car the rest of the chemical energy is converted mostly into heat and sound energy.
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State the process of energy input and output?
Energy input ---> useful device--->wasted energy to heat and sound and ---> useful energy output.
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Finish the sentence---> the less energy that is wasted the more____ the device is said to be.
The less energy that is wasted the more efficient the device is said to be.
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What is the equation for working out efficiency?
efficiency = useful energy output/ devided by/ total energy input x 100%.
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What must you do to find out the effficiency of a machine (to put into the equation)?
Find out the total energy input - this is supplied to the machine, then find out how much useful energy the machine delivers - useful energy output, which is the waste e.g. heat/ sound. And use efficiency equation.
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Example - An ordinary light bulb is 5% efficient. If 1000 J of light energy is given out, how much energy is wasted?
Total output = useful output/ efficiency = 1000 J / 0.05 = 20 000 J, so energy wasted = 20 000 - 1000 = 19 000 J.
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What is a sankey diagram?
They are energy tranformation diagrams - they make it easy to see at a glance much of the input energy being usefully employed compared with the amount wasted.
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What does the thicker arrow mean and the smaller arrow?
The thicker the arrow the more energy it represents - so you see a big thick arrow going in equals high input. Smaller arrows going off will show the different energy transformations taking place e.g. converting to heat or sound.
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For example questions on the sankey diagrams .....
Look in revision guide page 16.
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What do waves have?
Amplitude, wavelength & frequency.
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Draw an annotated diagram of a wave length.
Check with diagram on page 17 of physics revision book.
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What is the amplitude?
It is the dsiplacement from the rest position to the crest (NOT from trough to crest).
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What is the wave length?
It is the length of a full cycle of the wave from crest to crest.
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What is frequency?
The number of complete cycles or oscillations passing a certain point per second.
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What is frequency measured in?
Hertz (Hz) 1 Hz is one wave per second.
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What is the equation for wave speed?
Wave speed = frequency X wave length.
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What is speed, frequency, and wave length measured in?
speed = m/s Frequency =Hz Wavelength = M
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Example - Eva is building a sand castle. She estimates that 1 wave passes her sand castle every 2 seconds, and that the crest of the waves are 90cms apart. Calculate the speed in m/s, of the wave passing the sand castle.
Speed equals 0.5 X 0.09 = 0.45 m/s (remember to change the 90cms into metres first)
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What do we have to remember in all equations?
...to convert the units...
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what can all waves be ?
diffracted, refracted and reflected.
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what do waves travel in?
straight lines.
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what happens when a wave hits an object?
the direction of travel can be changed.
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what is reflection and what happens during reflection?
reflection of light allows us to see objects.Light bounces off them and into our eyes.
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What happens when light reflects off an uneven surface?
An un even surface such as paper- the light reflects at different angles.
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What happens when light reflects off an even surface?
like a plane mirror it all reflects at the same angle and you get a clear reflection.
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what does the angle of incidence equal?
angle of incedence = angle of reflection. These are always defined by the normal.
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what does total internal reflection depend on?
the critical angle.
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A wave hitting the surface can experience total internal reflection.. but when can this ONLY happen?
when travelling through a more dense object; like glass, water or perspex towards a less dense object such as air.
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complete the sentence- if the angle of incedence is big enough ...
the ray doesn't come out at all, but reflects back into the material.
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what does every material have?
a different critical angle.
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What happens to all waves when they pass through a gap or pass an object?
The waves diffract/spread out when they pass through a gap or pass an object
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What does does the amount of diffraction depend upon?
It depends on the size of the gap relative to the wavelength of the wave
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When a wave is diffracted, what 2 factors cause the wave to spraed out more?
The narrower the gap and the longer the wavelength are the 2 factors that result in greater spreading out of the wave
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What is considered a narrow gap in terms of diffracting a wave?
A narrow gap is one that is about the same size as the wavelength of the wave being diffracted
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Why is it difficult to diffract light?
To diffract light you need a very small gap (one equal to the wavelength of light @ 0.0005nm)
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Why can you hear someone through and open door when you can't see them?
The gap is too big to diffract light but the gap will be about the right size to diffract sound (longer wavelength) so that it fills the room
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How do the wavelength and size of the object interact for diffraction around an object?
The wider the object relative to the wavelength of the light, the less the diffraction
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What is Refraction?
Refraction of a wave is the changing of a wave's speed and direction as it strikes an object at an angle and moves from one substance to another of a different density
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In what direction does the wave get refracted when it travels from less dense to a more dense medium?
It slows down and gets refracted towards the normal
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In what direction does a wave get refracted when it travels from a more dense medium to one less dense?
It speeds up and gets refracted away from the normal
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Does a wave get refracted if it hits a medium when travelling along the normal (ie head on)?
No. It will change speed, but it will not change direction and so will not be refracted
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What types of waves can be refracted?
All waves can be refracted (sound, light, water etc) as long as the meet the boundary at an angle
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Name the 7 types of electromagnetic wave, in order (from long wavelength to short wavelength)?
Radio Waves, Micro waves, Infra red, Visible light, Ultra violet, X-Rays, Gamma rays
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What is the collection of Electrromagnetic Waves comonly known as?
The Electromagnetic Spectrum
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What is special about all electromagnetic waves travelling through a vacuum?
All electromagnetic waves travel through a vacuum at the same speed
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What is the relationship between wavelength and frequency for electromagnetic waves?
Shorter wavelength waves have higher frequencies
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What properties of EM wavelength are affected by changes in its frequency and wavelength?
The way the wave is REFLECTED, ABSORBED or TRANSMITTED by any given substance changes
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What is a general rule about the absorption of EM radiation?
Those waves at either end of the spectrum tend to pass through objects, those nearer the middle tend to be absorbed
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What EM radiation is the Sun's radiation made of?
50% of sunlight is visible light, most of the rest is Infra Red (heat) or UV. It is UV that gives us a tan
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Which type of EM radiation is the most dangerous?
EM radiation with the shortest wavelength (higher frequency) is the most dangerous as it contains the most energy
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What is the effect of absorbing EM radiation?
Absorbing radiation can cause heating and, if the frequency is high enough, ionisation. Ionisation is when an atom or molecule gains or loses electrons. It can be dangerous.
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Name some different uses for EM radiation?
Heating (infra red), cooking (microwave), Communication (radio waves for radio, microwaves for mobiles)
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Name 2 advantages of using wires for communication?
Electrical and optical wires can carry a lot of information; wires are secure (can't easily be broken into)
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Name a disdvantage of using wires for communication?
The can be broken and can be difficult to repair
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Name an advantage to wireless communications?
Wireless communication is portable (can be carried around...mobile phones, laptop wi-fi etc)
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Name 3 disadvantages of wireless communication?
Wireless signals can be intercepted; it is reliant on an aerial to pick up a signal; signal strength can be dependent on location
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Historically, why was communication with light used?
It enabled communication to speed up over long distances
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What is the priniple behind Morse Code?
By creating a code of on/off signals a message could be relayed between stations by flashing light on and off in a way that could be decoded
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Which too symbols are used in Morse Code?
Dots and dashes
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What is the international Morse Code distress signal?
SOS - 3 dots, 3 dashes, 3 dots
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Of what type of signal is Morse Code?
It is a type of Digital Signal because the light pulse is either on or off
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How does an optical fibre work?
Pulses of light or Infra red radiation enter the fibre at an angle greater than the critical angle so it is all reflected off the inside boundary of the narrow core. It then bounces form one side to another all the way down the fibre
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What is the principle that makes fibre optic transmission possible?
Total internal reflection of the light/IR pulses
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How quickly does light travel in a vacuum?
300,000,000 m/s
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How fast does light travel down optical fibre?
Light loses about 30% of its speed compared to travelling through a vacuum so it travels at about 200,000,000 m/s
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What is multiplexing?
Multiplexing means that lots of different signals can be transmitted down a single optical fibre at the same time so you don't need as many cables
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How big is an optical fibre that can take one million telephone calls at a time?
A fibre thinner than a human hair can take 1 million telephone calls at a time
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What is visible light made up of?
A combination of waves of different frequency and wavelength (and so colour) that are out of phase with each other (ie the crests and troughs don't match)
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What are the 3 special properties of a laser?
All the waves in a laser beam are the same frequency (and wavelength)and so it is monochromatic;all waves are in phase (troughs and crests line up); there is low divergence - the beam is narrow and stays narrow
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How does a CD work?
The surface of the CD has pits and lands (pits being slightly deeper than the lands). The laser is reflected back from land and pit slightly differently. It is the change in reflection that represents an "on", no change represents "off"
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Name 5 uses for Infra Red (IR) radiation
Cooking (grills and toasters); TV/DVD Remote controls;mobile phone/computer communications (short distance only); security sensors (sensing intruder body heat);instead of visible light in optical fibres
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What is infra red radiation also known as?
Heat Radiation
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What happens to the radiation given off as an object gets hotter?
The hotter an object, the more infra red radiation it gives off
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Why is infra red radiation useful?
Infra red monitors can determine how hot something is. So they can monitor heat loss from houses for example
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How do night vision devices work with infra red radiation?
The infra red radiation received is turned into an electrical signal which is displayed on a screen as a picture. The hotter the object is, the brighter it appears
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Who use infra red night vision equipment?
The police and the military
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How does a remote control work?
The remote sends polses of light. The pulses flash on and off in a coded sequence like Morse code. The device decodes the sequence and carries out the instructions associated with it
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Name 2 drawbacks of IR communication
The distance it can cover is small as the IR beam from a small device such as a remote is fairly weak. You have to point the beam directly at the receiving device as IR beams only travel in a straight line
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Why are Radio and microwaves good for communication?
They don't get absorbed by the atmospher as much as those in the middle or high frequency end of the spectrum (High frequency waves would be dangerous at the power levels required to send them over long distances)
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What are Radio waves?
EM waves with a wavelength over 10 cm
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How do long wave (1 to 10 km) radio waves act?
They will diffract quite a lot and so can be bent around the curvature of the Earth. As a result they can be sent halfway around the world
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What radio waves are used for TV and FM Radio?
Very short wavelengths (10cm to 10m) are used. These wavelengths do not bend around hills or travel far through buildings and so the aerial needs to be in direct sight of the transmitter
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How far can short waves (10m to 100m) travel?
They can travel quite long distances as they are reflected off the ionosphere. The shorter of the medium waves can also be reflected in this way, depending on atmospheric conditions
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How do obstacles affect long wavelength waves?
They can be diffracted around obstacles (you get more diffraction where waves are much greater in relation to the obstacle). Therefore, a long wave could be diffracted down into the foot of a mountain or valley
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How do obstacles affect short wavelength waves?
Short wavelength waves do not diffract as much so they need to be sited on high ground in order to clear obstacles and even then, they can only cover short distances. They may not be able to get down into valleys etc unless in line of sight
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Why might you get signal loss from a transmitting dish?
You may get diffraction at the edge of a transmitting dish and this will result in a weaker signal
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How does refraction occur in the high atmosphere?
Refraction is when a wave changes speed and direction when it hits a boundary at an angle. Boundaries are made in the atmosphere by the sun's UV radiation stripping electons form molecules to create the ionosphere
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How are short (10m -100m) and medium waves (300m) affected by refraction?
They are affected most by refraction and are, effectively, bounced back or reflected back to earth. This means these waves can be received a long way from the transmitter
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What factors affect refraction of radio waves?
Refraction is affected by frequency and the angle of elevation. Short waves do not refract as much as medium waves
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In what way do radio waves act like light waves?
Radio waves bounce off the ionosphere in the same way that light waves totally internally reflect inside optical fibres
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Name one problem with radio wave refraction?
The radio wave can be refracted away from the receiving dish
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Why don't nearby radio stations transmit at similar frequences?
Interference. There are a limited number of analogue frequences. If stations use similar ones the waves can combine to cause noise
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How does DAB work?
Many different signals are compressed and combined (known as multiplexing). They are transmitted across a relatively small frequency bandwidth and separated out by the receivers at the other end
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Why is multiplexing useful for DAB radio?
Many signals can be sent at the same frequency reulting in the potential for many more stations
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Why can DAB radio sound quality often be not as good as traditional FM radio?
This can be due to the compression of the signal
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What is the difference between microwaves in ovens and communications?
Microwaves in communications need to be of a wavelength that can pass easily through the watery atmosphere without being absorbed easily
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How does satellite communication work?
The signal is sent into a space from a transmitter where it is picked up by a dish on an orbitting satellite and then sent back in another direction from the sattellite's transmitter
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Microwaves are used for remote-sensing satellites ... what for?
To see through clouds and monitor oil spills, track the movement of icebergs, see how much rainforest has been depleted and so on
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How do mobile phones use microwaves?
Mobiles pass microwave signals to the mast (receiver). Masts pass signals between themselves and then on to the receiving phone
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Why don't microwaves diffract much?
They have shorter wavelengths than radio waves and so don't diffract as much
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What impact does their shorter wavelength have on microwaves?
They are affected by the curvature of the earth as they don't bend round it and they are blocked by large objects as they don't bend round them
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Where do microwave transmitters need to be postioned because of the impact of their short wavelengths?
As the waves don't diffract, the transmitters tend to be in line of sight, high up on hills and close together. If there is an obstacle between phone and transmitter, you may get a poor signal
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How are microwaves affected by water?
They are partially absorbed by water even though they can pass through the atmosphere. Therefore, they can be affected by bad weather or near lakes - resulting in poor signals
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Why is Satellite TV affected by stormy weather?
The increased water in the atmosphere absorbs the signal more resulting in a poor reception
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What can affect microwave signal strength?
Interference and water in the atmosphere
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How do microwave ovens work?
The microwaves are of a wavelength that is absorbed by water. The microwaves heat up the water in the item being cooked
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How will the microwaves from an oven affect tissues?
The water in them will absorb the energy and the cells may be burned or killed
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Do the microwaves from mobile phones harm people?
There is no conclusive proof that they are harmful. Studies so far have given conflicting results
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What care should be observed when using mobile phones?
We must balance the risks of using mobiles too much and locating masts close to poulated areas for stronger signals with potential harmfull effects of such prolonged exposure
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What are the 2 ways of sending sound and images?
Analogue and digital
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What is the difference between analogue and digital signals?
An analogue signal varies contnuously and can vary in both amplitude and frequency. A digital signal can have one of only 2 values - on or off
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Why do electrical signals need to be amplified?
Signals weaken as they travel
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What is interference?
When 2 or more signals of a similar frequency meet they can combine to create a signal with a new amplitude
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What problems can there be with amplifying an analogue signal?
When you amplify an analogue signal you also amplify and interference or noise. With a digital signal it is easier to ignore or remove the interference when it is amplified
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State 2 advantages of digital over analogue signals
Digital signals are easier to amplify without amplifying the noise and digital signals can be multiplexed (many signals send down a cable at the same time)
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What are the bad effects of sunlight?
Sunlight contains harmful UV rays which can damage DNA and cause skin cancer and eye problems such as cateracts
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How does darker skin protect you?
It absorbs more UV radiation and stops it getting to the more vulnerable tissues deeper in the body
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What does SPF 15 mean?
SPF means Sun Protection Factor and 15 means that someone wearing it can spend 15 times more time in the sun than if you were not wearing it before you burn
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How are we informed of the dangers of UV radiation?
Research is made public in the media and advertising campagns, the Government tells people how to keep safe and improve public health
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What is Ozone?
It is a molecule made up of 3 Oxygen atoms
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Where is Ozone found and what does it do?
There is an Ozone layer high up in the atmosphere and it absorbs some of the sun's UV radiation and stops it getting to the Earth's surface
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What has happened to the Ozone layer?
It has become thinner as gases called CFCs have been released into the atmosphere and reacted with the Ozone molecules to break them up
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Where is the hole in the Ozone layer and what happens to it?
There is an area over Antartica where the concentration of Ozone diminishes in the special winter weather. It increases again in Spring but the winter concentration has been dropping
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How do we know CFCs were bad for the Ozone layer?
Many studies have been conducted which concluded that CFCs were responsible. As a result, CFCs have have been banned internationally from hairsprays and fridge coolants
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What is good and bad a bout sunlight?
A little sunlight is good as it makes the body produce vitamin D but too much is bas as it can give you skin cancer
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What are seismic waves?
They are waves that travel through the earth. They are used by scientists to study the structure of the earth
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When are seismic waves produced?
When there is an earthquake, shockwaves are produced
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How do seismic waves help scientists?
Seismologists record the time it takes for these waves to travel from the source to the recording macjhine (seismograph). They also measure places that receive no waves at all
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What are the 2 types of seismic wave?
P waves (they have vibrations along the direction of travel of the wave); S Waves (have vibrations at right angles to the direction of travel)
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What are the differences between the travel of P and S waves?
P waves travel faster than S waves and also travel through liquids and solids (but S waves only travel through solids)
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Which parts of the earth can P waves travel through?
P waves travel through all parts (crust, mantle and solid inner core as well as the liquid outer core) - S waves can't travel through the liquid outer core
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How do seismic waves change with increasing depth?
They curve (refraction) with increasing depth as the properties of the mantle and core change. Most of the time they change gradually (curve) but when properties chnage rapidly, the wave speed changes abruptly and the path kinks
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Card 3

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Card 4

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What is temperature a measure of?

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What happens when a substance is heated?

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