P7

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  • Created by: Faith16
  • Created on: 01-12-15 19:47
What is a sideral day?
The time taken (23 hours and 56 minutes) for a star to reach the same position in the sky
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What is a solar day?
The time taken (24 hours) for the sun to reach the same position in the sky
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Why are solar days longer than sideral days?
A solar day is longer as the earth orbits the sun in the same direction as it spins. Therefore it takes slightly more than 360 degrees for the sun to appear in the same position.
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True or False. The moon glows by itself?
False- it reflects light from the sun
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Why can we only see certain parts of the moon?
Due to the moon orbiting the earth so we see different parts of the moon being lit up by the reflection of the sun
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Explain what a lunar eclipse is.
When the earth blocks any sunlight from getting to the moon so there is almost no light on the moon
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Explain what a solar eclipse is.
When the moon is just the right size and distance away to block out the sun.
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Why don't total eclipses happen very often?
As to get a total eclipse the sun, moon and earth all need to line up which doesn't happen very often.
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What is the pole star?
It is one of the two fixed postitions which was chosen as it doesn't seem to move as it is directly above the North Pole
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What is the celestial equator?
It is the other fixed position and is an imaginary plane running across the sky extending out from the earth's equator
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What are the two angles used to measure postions in the sky?
Declination (Celestial latitude measured in degrees) and Right Ascension (Celestial longitude measured in degrees or time)
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Explain retrograde motion.
This is where a planet is seen to go in a loop or squiggle. This is because earth is closer to the sun so it has less to orbit than other planets so when earth over takes them they seem like they are traveling backwards.
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What planets can we see from the 'naked' eye?
Mercury, Venus, Mars, Saturn, Jupiter
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What happens when the speed of light changes?
The wavelenght must change (wave speed= frequency x wave lenght)
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What happens if a light wave hits a boundary 'face on'?
The light wave slows down but carried on in the same direction. Shorter wave lenght but same frequency.
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What happens if a light wave hits a boundary at angle?
Part of the wave hits the boundary first and slows down while the othe rpart carried on at tfirst (faster speed for a while). This means that the wave changes direction (it has been REFRACTED)
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Why can triangluar prisms refract light to form a spectrum?
The boundaries aren't parallel which means the different wave lenghts don't recombine so you get a rainbow effect (spectrum)
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Explain what a convex lens does.
It causes the light rays to converge to a focus
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What is a principal axis?
A straight line that passes through the middle of the lens
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What is the focal point?
The focal point of the lens is where rays initially parallel to the principal axis meet.
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What is a focal lenght?
The distance between the middle of the lens and its focal point. The more powerful a lens the more strongly it converges light so the shorter the focal lenght.
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How do you make a lens more powerful?
The more curved a surface is the more powerful it is
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Describe a simple refracting telescope.
It is made up of two lens, a objective lens and an eye lens. The objective lens collects the light from the object being observed and forms and image which the eye piece magnifies.
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Why are the lenses aligned?
So that they have the same principal axis and are placed so that their focal points are in the same place.
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Why do most astronomical telescopes use a concave mirror?
As it is more curved so it is easier to see furhter away objects. Also making large lenses are difficuklt and expensive whereras a big mirror is easier to make more accurate.
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What is diffraction?
Where all the waves mspread out at the edges when they pass through a gap or past an object.
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What changes the amount of diffraction?
The size of the gap relative to the wavelenght of the wave. The norrower the gap or the longer the wavelenght the more the wave spreads out.
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What is the diameter of the objective lens called and why is it used?
It is called the aperture and it used to collect enough radition from distant and faint objects so that a better image can be formed.
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Why must the aperture size be larger than the wavelenght?
Because all the waves can diffract when they pass through a gap, radiation entering a telescope spreads out at the edges of the aperture causing the image to blur.
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How can diffraction grating be used to make a spectrum?
As white light passes through very narrow slits making it diffract but by different amount. This creates a spectrum. This is used to analyse the light coming from stars.
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Explain a parallax angle.
The parallax angle is half the angle moved against distat background stars over 6 months. The nearer an object is to you, the greater the angle.
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What is a parsec?
A unit of distance for objects that are very far way (1 parsec = about 3 light years)
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What does luminosity depend on?
Size and temperture- the bigger and hotter it is the more engery it gives out so the brighter it is.
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Explain Cephieds Variable Star's Pulse.
A group of stars get brighter and dimmer over a period of several days. How qucikly they pulse depends on their luminosity. The greater the luminosity, the longer the time between pulses ( the pulse period)
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Shapley's arugment was?
The Universe was one giantic galaxy. Our Sun and Solar System were far from the centre. The nebulae were huge cloyds of gas and dust which were part of the Milky Way.
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Curtis' arugment was?
The Universe was made up of many galaxies. The Sun was at or very near the centre of our galaxy. The spiral nebulae were other very distant glaxies separate from the Milky Way.
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Who was right from the Curtis-Shapley debate?
Shapley was right about the Solar System and how far from the centre out galaxy was. But Curtis was right that there are many galaxies and that the spiral nebulae were other galaxies.
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What is red shift?
The further away a galaxy is from us the redder the light appears as it reaches Earth. The further away a galaxy is, the faster it is moving away from us.
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What is the kinetic theory?
Gases consist of very small particles which are constantly moving in completely random directions.
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What happens if you increase the temperature of something?
You give the particles more kinetic energy so they more or vibrate more.
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What is absolute zero?
The coldest something can get (-273 celsius). At this temperature the atoms have as little kinetic energy as possible.
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How do you convert degrees Celsius to kelvin?
Add 273 (convert kelvin to degrees Celsius subtract 273)
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Kinetic engery is proportional to?
Temperture. The temperature of gas (in kelvins) is proportional to the average kientic energy of its particles.
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What pressure do gas particles give off when in a container?
Gas partilces crash against the containers walls creating an outward pressure.
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What happens if you change the volume of a container of gas particles?
In a bigger container the pressure decreases but in a smaller container the particles are more squashed up so they hit the walls more frequently causing a pressure increase.
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The volume of gas is inversly proportional to?
Its pressure at a constant temperature.
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Pressure is proportional to?
Absolute temperature. The higher the temperature the more kinetic energy the particles have.
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Volume is proportional to?
Absolute temperaure. If the gas stays at a constant pressure then heating it up increase its volume the molecules are further aoart so collisions happen less frequently but with more force.
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What is fusion?
Two nuclei can combine (fuse) to create a larger nucleus- nuclear fusion
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How does fusion work?
Energy is liberated (realsed) when lighter (smaller) nuclei fuse to make heavier (larger) neclei up to the size of an iron nuclues.
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What does E=mc squared stand for?
Energy realsed+ amount of mas lost X speed of light in a vacuum squared
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What is line spectra?
When electrons move between energy levels to gain or lose energy. If an electron gains enough energy to be removed from the atom it is called ionisation.
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Explain absorption spectra.
At high temperatures electrons become excited and jump into higher energy levels by absorbing radiation.There are only certain energy levels an electron can occupy, electrons absorb a particular frequency of radiation to get to a higher energy levels
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Explain emission spectra.
Electrons are unstable in the higher energy levels so they fall from higher to lower levels losing energy but emitting radiation of a particular frequency.
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What is the visable difference between emission and absoption spectra?
Absorption makes dark lines in continous spectrums. Emission gives a series of bright lines formed by the emitted frequencies.
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How does a star begin?
It starts as a cloud of dust and gas then gravity causes denser regions of the cloud to contract into clump creating a protostar.
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How does a star get to main squence?
The protostar collapses under gravity reducing in volume which causes the pressure and temperature to increase. When the temperture is high,hydrogen fuse to make helium it stops the gravitational collapse but sending a mass amount of energy outwards.
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What happens in the core of a star?
This is where the fusion happens. The pressure from the weight of the rest of the star makes the core hotter and denser than the rest of the star. This is so the nuclei in the core are close enough to fuse together.
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What happens on the photosphere of a star?
This is where the energy is radiated into space. Energy released from fusion in the core is transported by photons of radiation and convection currents to the surface pf the star. This is the part of the sun we can see from Earth.
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What is the life cycle of a red giant?
Small star- red giant- white dwarf. Doesn't have enough mass to compress the core so no more nuclear fusion occures. The outler layers of the star are thrown into space and the core of the star shrinks turning it into a hot white dwarf.
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What is the life cycle of a red supergiant?
Red supergiant- Supernova-Neutron star or black hole. A red supergiant has enough mass to carry on fusion. The core grows smaller being able to fuse elements until it gets to iron. This causes it to explode into a supernova.
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How is a neutron star or black hole formed?
When a supernova occurs the core then collapses to create a neutron star, or if there is enough mass a black hole.
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What is the Hertzsprung-Russell Diagram?
Luminosity of stars are plotted against the temperature. On the diagram these are put into 3 different groups: red giants and red supergiants, main squence stars and white dwarfs. Supernovas are not plotted as they are too quick to see.
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List advantages of computer controlled telescopes.
Can track objects in the sky, can scan across large areas of the sky to find a particular object, more precise, can be controlled over the interenet, can observe an object continuously, record and process data and can control telescopes in space
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What stops astronomers from getting accurate measurements?
Atmosphere only lets in certain wavelenghts e.g. radio waves are fine but visable light is badly affected. Light gets refracted by water which blurs the image and absorbed by dust particles in the air.
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How do you get around blocked electromagnetic radiation?
Put telescopes in space (e.g. Hubble in 1990)
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Why do space programmes always have cut-backs?
Due to the government having to pay for other things such as defence, healthcare and coping with natural disasteres
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Why are optical (visable light) observatories often in remtoe locations?
To try and avoid man made light pollution, dust and other particles that will affect the observations.
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What aspects are included when choosing telescopes locations?
High elevation ( atmosphere is thinner so affects light less) Dry location with low atmospheric pollution(water refracts light) areas that have a alot of cloudless nights ( clouds block a telescopes view)
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C.A.E.S?
COST- building running and eventually closing ACCESS- Site will need roads as well as electricity and other facilities ENVIRONMENT- damage the surrounding environment as little as possible SOCIAL- People need water, electricity, accommodation,shops
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Card 2

Front

What is a solar day?

Back

The time taken (24 hours) for the sun to reach the same position in the sky

Card 3

Front

Why are solar days longer than sideral days?

Back

Preview of the front of card 3

Card 4

Front

True or False. The moon glows by itself?

Back

Preview of the front of card 4

Card 5

Front

Why can we only see certain parts of the moon?

Back

Preview of the front of card 5
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