# core science physics part one

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• Created by: helen19
• Created on: 06-06-13 17:29
Describe the main features of the geocentric model.
The sun, moon, planets and stars all orbit the Earth in perfect circles.
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Explain how Galileo's observations of Jupiter proved the geocentric model wrong.
Galileo was observing Jupiter when he saw three star in a near line near the planet. When he looked again he saw these stars had moved in the wrong direction in the night sky. he realised not everythimg orbited the Earth
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How are we able to see stars?
Stars give out visble light thats why we can see them
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How are we able to see planets?
they reflect the suns light
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Write down two formulas for the speed of a wave.
speed=frequencyXwavelength or wave speed= distance/time
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Find the wavelength of a wave with frequency 15MHz and speed 3X10r8
5X10^8
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What happens to a light ray as it travels from air from air to water at an angle?
when a ray hit a boundary between two medium the light energy is reflected
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What is meant by focal point?
Where rays hit the lens parallel to the axis all meet
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How can you work out the focal length?
measure the distance from the lens to a sheet of white paper/card with the clearest imsge of the object on. how ever far away from the lens is your focal length
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Explain how an object's distance from a lens affects what image you will see.
An object nearer to the lens than the focal point wont appear on a screen on the same size of the lens. while an object between the focal point and 2X the focal point will be beyond the 2X the focal length on the opposie side of the lens
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How mant converging lenses does a refracting telescope use?
It uses two converging lenses (eyepiece lens and objective lens)
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How does a refracting telescope work?
The objective lens refracts the rays to form a real image at the focal point. The eyepiece spreads out so they leave at a larger angle and also makes the image look bigger (magnified)
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Explain how a reflectin telescope works.
A large mirrorreflects the light rays onto a smaller mirror in front of its focal length. The smaller mirror reflects the light rays back out through a small hole and into the eye
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List the seven types of electromagnetic radiaton in order of increasing frequency.
Raidowave(1m-10^4m), microwave(10^-2m), infrared(10^-5) visable light(10^-7), ultraviolet(10^-8), x-rays(10^-10), gamma rays(10-12)
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which type of Em radiation has the highest frequency?
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Describe how Herschel discovered infrared radition.
he noticed the highest temperature was the red end of the visible spectrum so he tested the temperature just beyond the red.
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why do some people worry about using mobile phones?
They use microwaves and they heat the humband body cells
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what can too much exposure to UV radiation cause?
It can give you bad sunburn, eye damage and skin cancer
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Give three ways to protect yourself from UV rays
You can wear suncream with high factors, wear sunglasses that protect your eyes from the UV rays and you can also just not stay out in the sun to long
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Explain how an optical fibre works
The waves bounce off the sides of a thin inner core of glass or plastic. the wave enters one end of the fibre and is reflected repeatedly until it emerges at the other end
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List five uses of infraredradiation around the home
Remote controls TV's and DVD players, cameras and toasters
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Describe what happens when UV light shines on a fluorescent material
When UV is absorbed and then visible light is emmited that's why fluorescent colours look so bright
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Describe how x-rays can help find a fracture in someones bone.
X-rays pass easily through flesh but not so easily through denser material like bone.The amount of radiation absorbed gives you the image.
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explain why radoitherapy treatment is directed carefully only at the tumour.
So they don't kill normal, health, non-cancerous cells.
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Give one advantage of irradiating food with gamma rays over other methods.
It doesn't involve high temperatures so they can totally sterilised without damaging them like boiling would.
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Name the three types of ionising radiation.
Gamma, alpha and beta
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What is ionising radiation emitted from?
At all times by radioactive sources when their nuclei decay.
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Compare the distances between the Sun andthe Earth with the distance between the Earth and the Moon.
The distance from Earth to the sun is 23000 times the radius of the Earth(6378km) and the Moon is only 60 times bigger than the Earths radius
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What is a galaxy?
A collection of billions of stars
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Describe the scale of the distance between galaxies.
Is often hundreds of thousands of times bigger than the distance between planets.
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What does SETI stand for?
Search For ExtraTerrestrial Intelligence.
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Suggest one type of information a space probe might collect.
Temperature
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Give two disadvantages of telescopes on Earth compared to space telescopes.
The Eaths atmosphere gets in the way and there is too much pollution.
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Explain why we need telescopesfor other parts of the EM spectrum, as well as visible light.
To get a full picture of the universe as possible.
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Describe what the absorption spectrum looks like.
It consists of light and dark lines.
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why does the absorption spectrum look the way it does?
The lines are caused by extra light being emitted at different wavelengths.
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Describe the first stage of a star's formation.
Clouds of dust and gas(a nebula) which is pulled together by gravity.
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Where does the initial energy come from?
The gravitational energy is converted into thermal energy.
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What is a main sequence star? How long does it last?
It enters a long stable period where the heat created by the nuclear fusion provides an outward pressureto balance the force of gravity pulling every thing in wards. This is main sequence.
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What happens after main sequence?
Eventually the hydrogen runs out and the star begins to swell into a red giant
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What are the final two stages of a small star's life?
The star becomes unstable and ejects its outer layer as a planetary nebula. This leaves behind a hot, dense solid core a white dwarf.
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What are the final two stages of a big star's life?
Glows brightly undergo more fusion forming heavier elements in various reactions until they explode in a supernova, which throws out it's outer layers forming a neutron star. if the star is big enough it will become a black hole.
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What is red-shift?
light from other galaxies
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Do galxaies furthur away have more or less red-shift then those nearer
More because they are furthur away so the light waves seem more spread out.
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What is the main theory for the origin of the universe?
The big bang theory
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Give two importanct bits of evidence for it.
It states that the universe is expanding which red-shift proves and the masses slow down the expantion.
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## Other cards in this set

### Card 2

#### Front

Explain how Galileo's observations of Jupiter proved the geocentric model wrong.

#### Back

Galileo was observing Jupiter when he saw three star in a near line near the planet. When he looked again he saw these stars had moved in the wrong direction in the night sky. he realised not everythimg orbited the Earth

### Card 3

#### Front

How are we able to see stars?

### Card 4

#### Front

How are we able to see planets?

### Card 5

#### Front

Write down two formulas for the speed of a wave.