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What did most ancient Greeks think about the Sun, Moon and stars?
That they all orbited the Earth
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What is this method known as?
The geocentric model
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What is the heliocentric model?
This states that the Earth and planets all orbit the Sun, which is at the centre of the universe
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What did Galileo find out with his telescope?
He saw three stars near Jupiter. When he looked the next evening, he saw the stars had moved in the wrong direction. He realised these weren't stars but moons that orbited Jupiter. This shows that not everything orbited the earth.
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Why can we see stars that are very far away?
Because they give off visible light
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Why can we see planets that are very far away?
Because they reflect the Sun's light
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What was used by the early astronomers to discover stars, comets and planets?
The naked eye
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What is wavelength?
The distance from one peak to the next
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What is frequency?
How many complete waves there are per second
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What is frequency measured in?
Hertz
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What does 1 Hz =?
1 wave per second
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What is amplitude?
The heigh of the wave
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What is the speed?
How fast the wave goes
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What don't waves transfer when transferring energy and information?
Matter
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In transverse waves the vibrations are at .... to the direction of travel of the wave?
90°
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In longitudinal waves the vibrations are along ..... ..... as the wave is travelling
Same direction
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What happens when a wave hits a boundary between one medium and another?
Some of its energy is reflected
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What is the angle of reflection the same as?
The angle of incidence
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Why is light reflected?
Because of the change in density
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Where can waves travel at different speeds?
In substances which have different densities
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What happens when light is shined on a glass window pane?
Some of the light is reflected but a lot of it passes through the glass and gets refracted
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What happens when light is passed from air to glass?
It slows down
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What does this cause?
The light ray to bend towards the normal
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What happens when th light is passed from glass to air?
The medium is less dense so it speeds up and bends away from the normal
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What is a real image?
Where the light from an object comes together to form an image on a screen
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What is a virtual image?
When the rays are diverging so the light from the object appears to be coming from a completely different place
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What does a converging lens look like?
It bugles outwards
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What does a converging lens cause?
It causes parallel rays of light to converge to a focus
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What is the axis of the lens?
It is a line passing through the middle of the lens
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What is the focal point?
Where rays hitting the lens parallel to the axis all meet
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Where does each lens have a focal point?
In front and behind
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What is a refracting telescope made up of?
An objective lens and an eyepiece lens
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Where will the incident ray parallel to the axis pass through when it's reflected?
The focal point
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Put these Electromagnetic waves in order: infra-red, ultra violet, gamma rays, radio waves, microwaves, visible light, x-rays
radio waves, microwaves, infra red, visible light, ultra violet, x-rays, gamma rays
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What type of wave are all EM waves?
Transverse waves
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What speed does all the EM waves travel at?
The same speed - 3x10^8 m/s
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How did Herschel find out about infra red?
He used a prism and a white light which would give off a spectrum of colours. He used a thermometer to find out each colour's temperature. He measured the temp of the part just past the red and the temp was highest. He found infra red
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What did Ritter want to find?
If there was anything on the other side of the spectrum beyond violet
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What did he do to experiment this?
Decided to measure how quickly silver chloride coated strips changed when exposed to different colours of light. In a dark room, he exposed the strips to each colour of spectrum. He timed them. Found quickest change was past violet - ultra violet
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As the frequency of EM waves changes...
its interaction with matter changes
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What are the EM waves at each end are supposed to be able to do?
Pass through material
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What are the EM waves in the middle supposed to be able to do?
Get absorbed
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What does the effects of EM radiation on humans depend on?
The frequency of the EM waves since frequency determines the energy of the waves
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The higher the frequency...
The more energy the radiation has and so more harmful the radiation
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How are microwaves harmful to humans?
Microwaves can heat human body cells. Because mobile phone usage has increased and is held quite close to the brin, it has been linked with many brain tumours but nothing has been proved yet
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How is infrared harmful to humans?
Has a higher frequency so it carried more energy. If the human body is exposed to infrared too much it can give nasty skin burns
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How is UV harmful to humans?
Has more energy and a higher frequency than infrared. UV can cause cell mutations or destruction and skin cancer. The UV can also cause eye damage
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How is gamma rays harmful to humans?
Can penetrate much further into the body than UV, infrared or microwaves. Can cause cell mutations or destruction leading to tissue damage or cancer.
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What are radio waves used for?
To broadcast TV and radio signals and to transmit satellite signals.
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What do long wavelengths do around the curved surface of the earth?
Bend
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Short-wave radio signals can be received at long distances from the transmitter. Why is this?
Because they are reflected from the ionosphere which is an electrically charged layer in the Earth's upper atmosphere
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Which wave is used for communication to and from satellites?
Microwaves
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What do microwaves do in microwave ovens?
The microwaves need to be absorbed by water molecules in food to be able to heat it up.
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What is infrared radiation also known as?
Heat radiation
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The hotter the object...
The more heat is given off
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What can infrared be used to monitor?
Temperature
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What kind of fibre can carry data over long distances as pulses of infrared radiation?
Optical fibres
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How do they work?
They bounce waves off the sides of a thin inner core of glass or plastic. The waves enter one end of the fibre an is reflected repeatedly until it emerges at the other end
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What uses does infrared have around the home?
Cooking, remote controls, mobile phone/ computers, security systems
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What happens when light enters your eye?
It gets refracted through the lens and focused onto the retina at the back of the eye. The retina then send messages to the brain and the brain interprets them
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Why do fluorescent colours looks so bright?
Because they actually emit light
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What do banks do to see if there are any forgeries?
They print special markings in fluorescent ink on their bank notes
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What does UV radiation do to water?
Disinfects water to kill off any viruses and bacteria in the water
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What are radiographers in hospitals used for?
Take x-ray photographs of people to see if they have any broken bones
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What do x-rays easily pass through?
Flesh
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What don't x-rays easily pass through?
Denser materials like bone or metal
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What can x-rays cause?
Cancer
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What do radiographers do to limit their exposure to x-rays?
Wear lead aprons and stand behind a lead screen or leave the room
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What good things can gamma rays be used for?
Treating cancers
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What precautions have to be done to kill the cancer cells?
The gamma rays have to be directed carefully and at just the right dosage without killing too many normal cells
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What does gamma rays do to food?
Food can be exposed to high dosages of gamma rays which will kill all microbes keeping the food fresher
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What should happen to the nuclei when an ionising radiation is emitted all the time by radioactive sources?
Decay
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Why is alpha, beta and gamma all ionising radiation?
Because they all transfer energy
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What do all planets orbit around?
Stars
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What do planets have often orbiting around them?
Moons
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What do scientists usually use to get some initial clues to see if there is anything beyond the solar system?
Earth-based telescopes or other remote-sensing techniques
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What does SETI stand for?
Search for Extra Terrestrial Intelligence
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What can robots do to analyse substances in space?
Take photos and collect soil and rock samples
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What did people back on Earth do with these samples?
They did experiments on it to see if they could find any signs of life
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What is the problem if you are trying to detect light through a telescope?
Earth's atmosphere gets in the way and it absorbs a lot of the light coming from space before it can reach us
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What other problems are there when trying to detect dim object?
Light pollution which is light thrown up into the sky from street lamps and air pollution can reflect and absorb light coming from space
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What was the name of the first telescope to be launched by NASA in 1990?
The Hubble Telescope
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What kind of telescopes were the earliest telescopes?
Optical telescopes
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What did they detect?
Visible light
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From the 1940s what was kind of telescopes were made?
Telescopes that can detect all parts of the EM spectrum
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What are x-ray telescopes good for?
Seeing violent, high-temperature events in space like exploding stars
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What were radio telescopes responsible for?
The discovery of the cosmic microwave background radiation
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What is used to analyse the light given out by stars and galaxies
A spectrometer
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How does a spectrometer work?
It works by the telescope directing a beam of light into the spectrometer and through a slit. This diffracts the light and splits it into a spectrum
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The light spectra from what contain dark lines?
From stars and galaxies
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What are these dark lines caused by?
The light at those wavelengths being absorbed. These patterns of dark lines are called absorption spectra
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What can absorption spectra be used for?
To work out what the stars and galaxies are made of
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What type of spectra have bright lines?
Emission spectra
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What are these lines caused by?
Extra light being emitted at those wavelengths
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What can emission spectra be used to work out?
To work out what something's made of
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Stars initially form from clouds of dust and gas called what?
Nebulas
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What does the force of gravity make the gas and dust do?
Spiral in together
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What does gravitational energy convert into to make the temperature rise?
It is converted into heat energy
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When the temperature gets high enough, what does hydrogen nuclei undergo?
Thermonuclear fusion to form helium nuclei and give out massive amounts of energy
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What does the star immediately enter?
A long stable period where the heat created by the nuclear fusion provides an outward pressure to balance the force of gravity pulling inwards
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What is the stable period called?
A main sequence star
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How long can a main sequence star last?
For several billion years
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What happens to the hydrogen eventually?
Run out
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What happens to the star when the hydrogen runs out?
The star swells into a red giant
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What happens to a small-to-medium-sized star when it becomes unstable?
It ejects its outer layer of dust and gas as a planetary nebula
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What does this leave behind?
A hot, dense solid core - a white dwarf
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What happens to the white dwarf eventually?
It would just cool down and disappear
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As big stars undergo more fusion, what happens?
It would start to glow brightly again and expand and contract several times, forming heavier elements in various nuclear reactions
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What would happen to the big stars eventually?
They'll explode in a supernova
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What does the exploding supernova do?
Throws the outer layers of dust and gas into space, leaving a very dense core
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What is this very dense core called?
Neutron star
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What would the star become if it gets big enough?
A black hole
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Are the frequencies lower or higher when we look at light from distant galaxies?
Lower
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What is this called?
Red-shift
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What does red-shift suggest to us?
That the galaxies are moving away from us
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What does red-shift provide evidence for?
That the universe is expanding
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What have scientists detected coming from all parts of the universe?
They have detected low frequency electromagnetic radiation
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Which part of the EM spectrum is the radiation mainly coming from?
Microwave
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What is this radiation known as?
The cosmic microwave background radiation (CMB)
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What is CMB radiation strong evidence for?
An initial Big Bang
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What is the theory of the Big Bang?
All the matter and energy in the universe must have ben compressed into a very small space. Then it exploded and started expanding
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True or False: The expansion is still going on
True
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What can we use to estimate the universe's age?
The current rate of expansion
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What is the Steady State theory?
That the universe has always existed as it is now and it always will do
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What does this theory explain about the expansion?
That the apparent expansion by suggesting that matter is being created in the spaces as the universe expands
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What is partial reflection?
This is when a wave passes from one medium into another, some of the wave is reflected off the boundary between the two media, and some is transmitted
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What does this mean?
That you can point a pulse of ultrasound at an object and wherever there are boundaries between one substance and another some of the ultrasound gets reflected back
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How can you measure how far away the boundary is?
The time it takes for the reflections to reach a detector
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What happens to the ultrasound waves when they reach a boundary between two different media?
Some of the wave is reflected back and detected
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What is the exact timing and distribution of these echoes processed by?
A computer to produce a video image of the foetus
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What do boats and submarines use to detect stuff underwater?
Sonar
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What does sonar do?
They emit waves of ultrasound which reflect off things like other boats, the sea bed and marine animals and detect these reflected waves as they arrive back at the boat
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True or False: Animals like bats and dolphins use ultrasound to sense their way around they environment
True
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What is infrasound?
Sound that has a frequency below the range of human hearing
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What is an advantage of infrasound?
They have long wavelengths so they can travel long distances and diffract around objects easily
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Approximately how deep is the Earth's crust?
20km
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What is below the crust?
The mantle
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What takes place within the mantle?
Radioactive decay
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What does radioactive decay produce?
A lot of heat which causes the mantle to flow in convection currents
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What is at the centre of the Earth?
The core
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True or False: The inner core is liquid
False - the inner core the solid. It's the outer core that's liquid
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The crust and the upper art of the mantle are cracked into a number of large pieces called...?
Tectonic plates
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What causes the plates to drift?
Convection currents in the mantle
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What causes an earthquake?
When the plates slide over each other
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What is produced when there's an earthquake somewhere?
Seismic waves which travel out through the Earth
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What do we use to detect these waves all over the surface of the planet?
Seismometers
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True or False: P-waves are transverse
False - P-waves are longitudinal. It's S-waves that are transverse
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What do P-waves travel through?
Solids and liquids
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What do S-waves travel through?
Solids only
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Are P-waves faster than S-waves?
Yes
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When seismic waves reach a boundary between different layers of the Earth, what happens to some of the waves?
Some waves will be reflected
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The waves change speed as what changes?
As the properties of the mantle and core change
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What does the change in speed cause the wave to do?
Change direction - refraction
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When most properties change suddenly the wave speed changes abruptly and the path has a what?
Kink
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What can seismometers be used to work out?
The distance to an earthquake's epicentre
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What do P-waves and S-waves stand for?
Primary and Secondary waves
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What can you use o calculate how far away the earthquake or explosion was?
The time difference between the two waves
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What is current?
The rate of flow of charge around a circuit
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What do electron usually carry?
The charge
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What charge is an electron?
Negative
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What is voltage?
An electrical pressure giving a measure of the energy transferred
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What is AC current?
Alternating current
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What is DC current?
Direct current
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Why are electrical appliances useful?
Because they take in electrical energy and convert it into other forms of energy
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What does the electrical power of an appliance tell you?
How quickly it transfers electrical energy
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What is electrical power?
The energy transferred per second
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What are the units for power?
Watts (W)
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The higher the power of your appliance...
...the more energy is transferred every second
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How can you induce a voltage or current in a conductor?
By moving a magnet in or near a coil of wire
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What is this called?
Electromagnetic induction
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As you move the magnet, the magnet field through the coil changes. What does this change in the magnetic field induce?
A voltage, and a current flows in the wire
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What happens to the current if you move the magnet into the coil?
The voltage and current are induced in the opposite direction from when you move it out of the coil
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What happens to the voltage and current if you reverse the magnet's North-South polarity?
The voltage and current are induced in the opposite direction
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What are the two ways you can create a voltage and current in a conductor?
By either rotating a magnet in or near a coil of wire OR by rotating a coil of wire in a magnetic field
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If you want a bigger peak voltage what do you at least have to increase?
The strength of the magnet, the area of the coil, the number of turns on the coil or the speed of movement
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What do you get if you move or turn the magnet faster?
You'll get a higher peak voltage and also a higher frequency
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How do generators generate alternating current?
By electromagnetic induction either by rotating a magnet or by rotating a coil of wire and keeping the magnet fixed
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What is a dynamo?
A particular type of generator which is often used of bikes to power the lights
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Name four non-renewable energy resources
Coal, oil, natural gas, nuclear fuels
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What do all three fossil fuels (coal, oil, natural gas) give out?
Carbo dioxide
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Which fossil fuel releases the most carbon dioxide?
Coal
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What does all of this carbon dioxide add to?
The greenhouse effect and causes global warming
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How can we stop some of it entering the atmosphere?
By "capturing" it and burying it underground
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What does burning coal and oil release?
Sulfur dioxide which causes acid rain
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How can this be reduced?
By taking the sulfur out before it's burned or cleaning up the emissions
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What does coal mining do to the landscape?
Makes a mess
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What does oil spillages cause?
Serious environmental problems
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True or False: Nuclear power is clean but nuclear waste is very dangerous and hard to dispose of
True
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Why is the overall cost of nuclear power high?
Because of the cost to build and decommission the power plant
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What does nuclei power always carry the risk of?
A major catastrophe like the Chernobyl disaster
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What does nuclear fission produce?
Heat to make steam to drive turbines
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True or False: Nuclear power stations take the shortest time of all the power stations to start up
False - It's natural gas power stations that take the shortest time to start up. Nuclear power stations take the longest time
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What is a renewable energy source?
One that will never run out
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What don't they provide much of?
Energy
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Why are some renewable energy unreliable?
Because they depend on the weather
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What does hydroelectric power usually involve?
Flooding a valley by building a big dam
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What is rainwater allowed out through?
Turbines
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What is an advantage of this?
There is immediate response to increased electricity demand
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Why is wave power fairly unreliable?
Because waves tend to die out when the wind drops
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What do most electricity generated from wave power use?
Waves close to the shore
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What are tidal barrages?
Big dams built across river estuaries with turbines in them
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What happens when the tide comes in?
It fills up the estuary to a height of several metres.
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How is the generator turned in wind turbines?
Each wind turbine has its own generator inside it so the electricity is generated directly from the wind turning the blade
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Give three disadvantages of wind turbines?
They spoil the view, can be very noisy and they only work when it is windy so it's not always possible to supply electricity
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What are solar cells usually used to generate?
Electricity on a relatively small scale
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Where is solar power often used?
In remote places where there aren't many other ways to generate electricity
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True or False: Geothermal energy is only possible in certain places where hot rocks lie quite near to the surface
True
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How is the generator driven?
Water is umped in pipes down to the hot rocks and it returns as steam
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What is a disadvantage of geothermal energy?
The high step cost and the fact that there are very few places where this seems to be an economic option
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What can biomass be?
Farm waste, animal droppings, landfill rubbish, specially grown forests etc
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Why is the waste material burnt in power stations?
To drive turbines and produce electricity
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True or False: The plants that grew to produce the waste would have absorbed carbo dioxide from the atmosphere as they were growing
True
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What happens when the waste is burnt?
The carbon dioxide is re-released into the atmosphere
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Why are many old coal and oil fired power stations being taken out of use?
Because coal and oil are running out fast
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What are they often being replaced by?
Gas-fired power stations because these are quick to set up
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What are the factors to consider when looking at the options for a new power station?
How much it costs to set up and run, how long it takes to build, how much power it can generate etc
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The bigger the power station...
...the more expensive
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Why do nuclear reactors and hydroelectric dams also need huge amounts of engineering?
To make them safe which increases the cost
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What do many of the renewable sources depend on?
The weather
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What are the environmental issues of energy resources?
Atmospheric pollution, visual pollution, other problems, using up resources, noise pollution, disruption of wildlife habitats
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What does the National Grid do?
Takes electrical energy from the power stations to just where it's needed in homes and industry
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What does it enable?
Power to be generated anywhere on the grid
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What do you need to transmit huge amounts of power?
A high voltage or a high current
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What is a problem with the high current?
You lose loads of energy through heat in the cables
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What is it much cheaper to do?
Boost the voltage up really high and keep current very low
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What is required to get the voltage to 400,000V to transmit power?
Transformers as well as big pylons with huge insulators
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For efficient transmission, what do the transformer have to do?
Step the alternating voltage up at one end and then bring it back down to safe, useable levels at the other end
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What are the two coils transformers all have?
Primary and secondary joined with an iron core
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How is the voltage increased?
Using a step-up transformer
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What is used to reduce the voltage at the consumer end?
A step-down transformer
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Primary voltage/secondary voltage=?
number of turns on primary/ number of turns on secondary
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What can you do to your house if you want to save money on heating bills?
Insulate the house
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What is payback time?
When the money you save on your heating bills will equal the initial cost of the insulation
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What is energy measured in?
Joules (J) or kilojoules (kJ)
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1kJ=?
1000J
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What does the amount of energy an appliance depend on?
Its power and the time you leave it on for
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What do electricity meters record?
How much energy you've used
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What is a kilowatt-hour?
The amount of energy used by a 1kW appliance left on for 1 hour
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What are the nine types on energy?
Kinetic, nuclear, chemical, heat, electrical, light, potential, sound, elastic
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True or False: Energy can be created and destroyed
False - energy can NEVER be created nor destroyed. It is only every transferred from one form to another
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What do electrical devices convert electrical energy into?
Sound, light, heat etc
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What do batteries convert chemical energy into?
Electrical energy to run electric devices
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What is the total energy output always the same as?
The energy input but only some of the output energy is useful
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Why is this?
Because some of the inout energy is always lost or wasted often as heat
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The less energy that is wasted...
...the more efficient the machine is said to be
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Efficiency=?
(Useful energy output/total energy input) x100%
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True or False: All objects are continually emitting and absorbing heat radiation
True
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When an objet is hotter than its surroundings does it emit more or less radiation than it absorbs?
More
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When an object is cooler than its surroundings does it absorb more or less radiation than it emits?
More
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What does the power of heat absorbed need to be the same as for an object to stay at the same temperature?
The power emitted
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Do dark matt surfaces absorb or reflect heat radiation?
Absorb
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Do glossy bright surfaces absorb or reflect heat radiation?
Reflect
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Card 2

Front

What is this method known as?

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The geocentric model

Card 3

Front

What is the heliocentric model?

Back

Preview of the front of card 3

Card 4

Front

What did Galileo find out with his telescope?

Back

Preview of the front of card 4

Card 5

Front

Why can we see stars that are very far away?

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