# Science Core - Physics 1

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• Created by: alliyah14
• Created on: 11-05-16 17:22
What is energy a measure of?
Energy is a measure of heat.
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When heating a subtance, What does the particles from that subtance gain?
Its particles gain Kinetic Energy (KE)
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What does Kinetic energy do to solids, liquids and gases?
Liquids & Gases Kinetic Energy causes them to move faster, whereas solids particles just vibrate quicker due to the kinetic energy. Liquids will boil where solids will melt.
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What is an absolute scale?
Energy is measured on an absoulte scale. Therefore the it can't go below 0 because there is a limit on how slow particles can move.
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What does temperature meaure?
Temperature is a measure of hotness. Or the average kinetic energy of a subtances particles. The hotter something is the higher the teemperature and the kinetic energy.
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Why doesn't temperature have an absolute scale?
This is because temperature can go below 0.
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How does energy tend to flow?
Energy tends to move from hot objects to cold ones. The greater the difference between the two objects temperatures the quicker the heat/energy will flow.
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What is Specific Heat Capacity?
Is the amount of energy needed to raise the temperature of 1kg of a subtance by 1*C. For example water is 4200J/kg
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Why is waters Specific Heat Capacity so high?
This is because water holds a lot of energy which makes it good for central heating systems
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How do you calculate Energy?
Energy = Mass x SHC x Temperature change
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How do liquids turn into gases?
When liquids are heated the particles move faster and eventually boiling, resulting in gases being formed.
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When heating a subtance what is the energy used for?
The energy is used to break the intermolecule forces rather than raise temperatures. This is represented through the flat parts of the graph (melting and boiling).
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When a subtances is condensing or freezing what is taking place in terms of bonds?
The bonds are forming between particles which releases energy. This means the temperature doesn't change until the subtances turns into a liquid (condensing) or soild (freezing).
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What is Specific Latent Heat?
The Specific Latent Heat is the amount of energy needed to melt/boil 1 kg of material without changing its temperature.
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During SLH why don't you include the temperature change?
The material should already be at melting/boiling temperature already.
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What is the formula for Specific Latent Heat?
Energy = Mass x Specifc Latent Heat
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How does conduction work?
In solids the particles are held tightly together so vibrations can be passed along easily. Particles which are quicker pass along their kinetic energy to neighbouring particles which continues throughout the solid increasing the temperature all over
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What is conduction of heat?
Conduction of heat is the process where vibrating particles pass on extra kinetic energy to neighbouring particles.
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Why do metals pass on heat so well?
This is because melts have lots of free electrons which transfer heat.
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Why are non-metals good insulators?
Most non-metals don't have free electrons so warm up slowly. For example handles on saucepans are non-metals so we don't get burned.
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Why do liquids and gases bad at transfering heat compared to solids?
Tis is because soilds have their particles held tightly together so can pass on kinetic energy easier. The particles in liquid and gases are not held tightly together.
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Where does Convection occur?
Convection occurs in Liquids & Gases
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What happens to Liquids and Gases when they are heated in terms of particles and density?
Their particles becme faster but also liquids and gases become less dense and expands.
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How does Convection work?
When Liquids or Gases are heated they rise above to the cooler surroundings and the cool air takes the place of the warm air/fluid. This process continues and you get a cycle.
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Why can't convection take place in solids?
Solids particles can't move so they would just vibrate on the spot.
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How do you reduce convection?
You need to stop the air or fluid from moving which can be done using insulators to trap air. This leads t the air not being able to move so heat must conduct slowly.
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What type of waves are used to get heat from the Sun?
Heat is radiated as infrared waves - these are electronmagnetic waves that travel in straight lines at the speed of light.
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How is radiation different from convection and conduction?
It can happen in a vacuum, Only can take place with transparent objects & The amount of radiation emitted or absorbed depends on surface colour and texture.
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What is the correlation between how hot an object it is and how much heat it emits?
The hotter an object gets, the more heat energy it emits.
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What features are best for absorbing and emitting heat?
Matt black surfaces are good at absorbing and emitting heat.
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Why are poor absorbers and emitters useful?
This is becasue they can reflect heat so that matt black surfaces can absorb and emit the radiation.
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What cooking methods use heat radiation?
Grills, Toasters and microwaves.
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How does Grilling and Toasting take place in terms on infrared radiation?
The foods surface absorbs the heat that is given off by the Grill or Toaster which increases the kinetic energy. This is then transfered to the middle of the food using convection or conduction.
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How does Microwaves heat food in terms of infrared radiation?
The microwaves (which are different to infrared) pentrate about 1 cm in the food. Then this heat is absorbed by water or fat molecules which increase kinetic energy. The energy is then transfer to the centre using conduction or convection.
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Why in a grill can you use shiny foil but not in a mirowave?
In a grill the foil reflects the radiation back to the bottom of the food, wereas in microwaves the waves will be reflected by the foil and the refletions can cause sparks.
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Why is it important to insulate your house?
To ensure that energy in the home isn't being wasted or lost.
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What are Sinks and Sources in terms of Insulating?
The sources are things that emit energy (radiators) & Things that transfer, lose or waste energy are known as sinks.
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What is payback time?
They money you have saved through energy billswill equal the intial cost.
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What are some methods to reduce Sinks (waste of energy)?
Loft Insulating, Hot Water Tank Jacket, Cavity Walls & Insulation, Draught-Proofing, Thick Curtains & Double glazing.
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How does Loft Insulation prevent loss of energy?
Wool is laid across the floor of the loft to reduce conduction through the ceiling.
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How does Cavity Walls & Insulation prevent loss of energy?
Two layers of bricks in walls with a gap inbetween but it could still loss energy due to convection. As a result insulate the gap using foam to trap pockets of air and minimise convection.
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How does Draught-Proofing stop loss of energy?
Strips of foam are located around the doors and windows to stop hot air going out.
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How does Thick Curtains prevent loss of energy?
Prevents hot air reaching the window by convection and reduces conduction.
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How is Double Glazing useful?
Two layers of glass with an air gap reduce conduction.
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On a thermogram what do the different colours represent?
Hot to cold: White, Yellow, Red, Purple, Blue & Black.
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How is efficiency calculated?
Efficiency = Useful Energy Output / Total Energy Input (x100%)
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Whta is a Sankey diagram?
Its a diagrm to tell you how much energy is useful & wasted from the input energy.
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What is the amplitude?
Is the displacement from the rest position to the crest.
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What is a wavelength?
It is a complete full cycle of a wave crest to crest.
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What is the frequency?
Its the amount of full cycles or oscillations passing a certain point per second.
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What is the formula for Wave speed?
Speed (m/s) = Frequency (Hz) x Wavelength (m)
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What can all waves do?
They can be reflected, Refracted and Diffraacted.
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How is reflection used to see objects?
The light allows us to see objects. Light bounces of surfaces and allows us to see them.
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What is the law of reflection?
Angle of incidene = Angle off reflection
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What does the total internal reflection depend on?
Total internal reflection depends on the critical angle.
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When does total internal reflection occur?
This can only happen when the light ray travels through a dense material like glass, water or perspex towards a less dense subtance like air.
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During total Internal Refletion what happens if the angle of incidence is big?
If the angle of incidence is big enough the ray doesn't come out at all and in fact reflects back into the material. However the icidence must be bigger than critical angle for that particular material - every material varys.
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In total internal refletion what happens if the angle of incidence is LESS than the critical angle?
Most of the light is refracted into the outer layer but some is internally reflected.
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In total Internal reflection what happens if the angle of incidence is EQUAL to the critical angle?
The ray would go along the line of critical angle with a little internal reflection.
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In total internal reflection what happens if the angle of incidence is GREATER than the angle of critical?
No light comes out, it is all internally reflected.
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What is Diffraction?
This is where the waves spread out (diffract) at the edges when they pass through a gap or object.
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What does diffraction depend on?
The amount of diffraction depends on the size of the gap relative to the wavelength of the wave. However the narrowness of a gap depends on how big the wavelength is. e.g light has a small wavelength so will need a very small gap to diffract.
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Why can you hear someone through a slighly open door but you can't see them?
You can hear someone due to the size of the gap and the wavelength of sound are roughly equal casing the sound to diffract thoughout the room. But you can't see them as the door gap is much bigger than the wavelength of light hence it won't diffract.
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How can you explain shadows using diffraction?
A shadow is where a wave is being blocked so the wider the obstacle (the thing that is blocking the light) compared to the wavelength there will be less diffraction so the longer the shadow.
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What is refraction?
Changing the speed of a wave can change its direction - Refraction
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What haappens if light hits a boundary face on?
It slows down but carries on in same direction. It now has a shorter wavelength and the same frequency.
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What happens if a wave hits a medium at an angle?
The wave will change direction because a part of the wave will slow down (the part that hit the water first) and the other will remain the same speed causing the wave to change diresction due to speed. - Refraction.
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What is the vitial condition needed for refraction to take place?
Waves are only refracted if they meet the medium at an angle causing parts of the wave to slow or speed up causing change in direction.
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How many types of electromagnetic waves (EM) are there?
7: Radio waves, Micro waves, Infrared, Visible light, Ultra violet, X-rays & Gamma
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When do EM waves travel at the same speed?
All EM waves travel at the same speed when in a Vacuum which means waves with smaller wavelengths have higher frequency.
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In EM waves which are absorbed, transmitted and reflected?
EM waves at each end of the spectrum are able to pass through material but ones in middles are usually absorbed.
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Ẁhy are waves with high frequency (short wavelengths) dangerouus?
This is because these types of waves have more energy and can harm living cells.
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What is ionisation?
This is where an atom or molecule loses or gains electrons.
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What happens when any EM radiation is absorbed?
When any EM radiation is absorbed it can cause heating or ionsation.
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Why is using light, radio and eletrical signals good for communication?
They are good because they are quick.
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Why use electrical wires and optical fibres?
This is because they can carry lots of information. Also because it is sent in a wire they are secure and can't be tapped into. Radio signals travel in the air so can be intercepted.
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What is a disadvantage of using caples?
They are difficult to fix and repair.
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What is a benefit of wireless communication?
It is portable but depends on the strength of the signal, which varies depending on location.
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What is Morse code?
The communication with lights using on-off signals (dots and dashes). SOS = ***---***
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How do optical fibres work?
The wave hits the core and outer cladding at a greater angle than the critical angle to cause total internal refletion, this happens many times until it reaches the other end.
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Where are Optical fibres used?
Telephones and broadband - replaing old ones. Also used for medical purposes to look inside the body without operating.
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What are some advantages of using light as communication?
Its very quick (but slowed down about 30% in a Vacuum). Also multiplexing means lots of different signals can be transmitted using on wire. Laslty its digital preventing interference.
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What do Lasers produce?
Lasers produce Narrow Intense beams of monochromattic light.
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What is the difference between visible light and lasers?
Visivle light has different frequency and wavelengths (and colour) so its 'Out of phase'. However lasers are same wavelength and frequency as a result its 'In phase'.
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What does monochromatic mean?
Just a complex way of saying pure and single. therefore a laser is just a single and pure colour wave.
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Why are laser beems known as coherent?
Because theey have a fixed phase difference. If a light has the crest and troughs line up then the fixed phase difference would be zero - the waves are in phase.
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What is meant by lasers are divergence?
The beam is narrow, and it stays narrow, even at long distances from the light source.
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How do CD players use lasers to read digital information?
CDs have millions of tiny shallow pits cut into it. The bits inbetween each pit is a land. A laser is shone on the bottom but the pit and land reflect it different which light sensors get. Diffrences is electrical signal which is turrned to sounds.
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What uses does Infrared Radiation have?
It can be used it cooking (Grills & toasters), remote controls, phones, computers (only short distances), security systems, monitor temperautre & sometimes through optical fibres.
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What is Infrared Radiation also known as?
Heat Radiation.
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How can Infrared Radiation monitor temperature?
If there is two object and one is hotter, that one will be giving out more radiation. So to see where heat loss is use infrared sensors because the more radiation the hotter the object is.
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How is infrared used in nightvision equipment?
The equipment uses electrical signal which displays on a screenas a picture. The hotter an object is (the more IR given of) the clearer the object appears.
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What are long wavelengths good for?
Long wavelengths travel well through earth's atmosphere, specifically radio waves and microwaves.
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Why can long wavelengths travel far distances?
This is because they don't get absorbed (only waves in the middle of the spectrum get absorbed) or thoses with high frequency.
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How can radio waves travel half way around the earth?
This is because they diffract (bend) around the earths curved surface of the earth.
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Why can't very short radio waves travel far?
This is because the waves can't diffract (bend) hence you must be directly opposite the transmitter to get a reception
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How can short-waves travel long distances?
This is because the radio waves reflect of the ionosphere. Othwer waves can reflect off the ionsphere but it all depends on the atmosphere.
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Why are long wavelengths useful during wireless communication?
This is because long radio wavelengths diffract (bend) hence traveling around obstacles. Therefere they can travel long distances without having to be in line of sight
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Why are short wavelengths so poor for wireless communication?
This is due to short wavelengths don't diffract much so they transmitters need to be located high in order to get a signal.
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How does refraction help waves travel further?
Refraction allows waves to travel at faster speeds so they can travel longer distances.
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What is the ionosphere?
Atoms that have either gained or lost electrons are created by the sun in the earths atmosphere using UV radiation. These ionised atoms are electrically charged and make a layer called the ionosphere.
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Why can short and medium wave lengths be received a long way away from a transmitter?
This is because the short and medium waves are reflected back to earth.
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What is a disadvantage of using refraction to communicate wirelessly?
It can disrupt signals by bending it away from the receiver dish.
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Why do analogue signals suffer from interference on the radio?
This is because analogue signals usually have similar waves covering a similar area which can combine and cause a 'noise'. This is why radio stations near each other must use different frequencies or they will interfere each other.
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What does DAB stand for?
Digital Audio Boardcasting
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What is multiplexing?
Many different signals are compressed together then transmitted as a single wave. DAB use this method.
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How does DAB separate the signals that are compressed during multiplexing?
The compressed signals are compressed across a small frequency bandwidth and separated by the receivers. The DAB radio set picks up the signal and decodes it.
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As DAB suffers from less interference how does this benefit the radio station?
Other than lack of interference, due to multiplexing more radio stations can come available.
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Why can't some areas use DAB?
This is because there is a limited number of DAB transmitters in the world so some areas can't recieve digital radio signals.
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Why isn't DAB sound quality as good as traditional FM radio Boardcasting?
It's because DAB compress many signals together so the quality is not as good.
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Why must you have the perfect wavelength when using microwaves for satellite communication?
This is because these waves must past through the earths watery atmosphere within beings absorbed.
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How do satellites help signals transmit all around the world using microwaves?
Microwaves are transmitted into space and then the dish orbiting the earth sends the signal back in a different direction where it's received.
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Why must microwave transmitters be positioned in line of sight when making a phone call?
Phones use microwaves which are shorter than radio and don't diffract (bend) so cannot get past certain obstacles. This means you need to be in line of sight to get a signal.
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Why do you lose signal when there is a storm?
This is because microwaves are absorbed by water so are therefore lost.
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What are some dangers of using a microwave?
Microwaves are absorbed by water so the food we eat has dangerous things in it that can harm our cells or maybe even kill them.
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Why is there arguements around mobile phone is causing damage to our health?
Some believ that it does but after lots of studies been carried out its found that there is no proof.
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Why must we balance the risk and benefit of technology?
As it could cause physical harm if you have prolonged exposure but it's allowed use to access information easily.
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Is there a correlation between size of receiver and size of wavelength?
Yes because the bigger the wavelength the bigger the recieve will need to be.
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Why does big wavelengths need big receivers?
This is because of diffraction, if it takes place detail could be lost. Therefore the gap in the receiver must be big enough for little diffraction to take place. Hence big wavelength = big receiver.
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Why are telescopes many different sizes?
This is because telescopes detect many different EM waves with lots of different wavelengths. Bigger the telescope = clearer.
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What is diffraction-limited?
Telescopes with small gaps compared to the wavelength have limited resolving power.
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Why do Optical mircoscopes have to be so small?
They are used to detect small tiny things. Therefore the gaps need to be really small so diffraction can take place due to the small wavelength of light.
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What needs to take place before information is transmitted?
The information must be converted into electrical signals.
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What are the two types of signals?
Analogue and digital
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What is the difference between analogue and digital signals?
Analogue is varied, whereas digital is on and off. Analogue can take any frequency or amplitude. However digital can only take on/off = 1/0
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Why do signals need to be amplified?
Digital and analogue signals weaken as they travel so need to be amplified.
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What happens when you amplify an analogue signal and how does it vary from digital?
The noise is also amplified making the signal lose quality, whereas the noise is easily removed from digital signals so remains high quality.
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What is interference?
When two or more waves of a similar frequency meet, they create one combined signal with a new amplitude.
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Which signal can multiplex? Analogue or digital?
Digital
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How can being exposed to the sun cause skin cancer?
Sun Ray's include UV Ray's which can damage the cells and also cause eye problems.
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Why are people of a darker skin more protected?
Darker skin absorbs more UV radiation this prevents more damaging radiation reaching vulnerable parts of the body.
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Other than the sun how are people being exposed to UV radiation?
Sun beds that's why you have a time limit so people don't harm their cells
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What protects us from UV radiation?
The ozone layer, found in the higher layer of the earths atmosphere.
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How does the ozone layer protect us from UV radiation from the sun?
The ozone layer is made up of three oxygen atoms that absorb UV to reduce the amount we are exposed to.
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Why is the ozone layer getting thinner?
Due to pollution of CFCs which break the ozone layer, as a result exposes us to more.
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Where is there a visible hole in the ozone layer during the winter?
There is a hole in Antarctica during the winter.
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What has been done to prevent more holes in the ozone layer?
Banning uses of CFCs in certain places.
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What are seismographs used for?
To measure the seismic waves produced by earthquakes and also the time it takes to reach a seismograph.
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Why are the two types of seismic waves?
P-waves & S-waves.
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What is a P-wave?
It's a longitudinal wave which are faster than S waves but only travel through solids and liquids. Unlike S waves they travel through the core.
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What is an S-wave?
It's transverse and the vibrations move up and down, whereas P waves go left to right. S waves only travel through solids and are slower than P. Hence they don't go through the core.
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What can P & S waves tell us about the structure of the earth?
The mantle is a solid as the S waves can pass through but the Core is a liquid as the S waves can't pass through.
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Why do the waves change direction in seismic waves?
This is because of refraction as the speed changes too.
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## Other cards in this set

### Card 2

#### Front

When heating a subtance, What does the particles from that subtance gain?

#### Back

Its particles gain Kinetic Energy (KE)

### Card 3

#### Front

What does Kinetic energy do to solids, liquids and gases?

### Card 4

#### Front

What is an absolute scale?

### Card 5

#### Front

What does temperature meaure?

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