Karteikarten
GCSE Physics P2 (OCR)
Karten in diesem Stapel (39)
- 1Explain how radiation travels.1) It is emitted by a source.
2) It can be reflected, transmitted or absorbed by materials it encounters.
3) It may effect a detector some distance away when it is absorbed. - 2How does electromagnetic radiation transfer energy?In packets called photons.
- 3The ________ the frequency of electromagnetic radiation, the _____ energy is transferred by each photon.Higher
More - 4List the electromagnetic radiations in order of the energy transferred by each photon.Radio Waves
Microwaves
Infrared
Visible Light
Ultraviolet
X-Rays
Gamma Rays - 5How quickly does each type of electromagnetic radiation travel through space?They all travel at the same speed, 300 000km/s.
- 6What is the intensity of a beam of electromagnetic radiation?The energy that arrives at a square meter of surface each second.
- 7What is the energy transferred dependent on?The number of photons arriving and the energy of each photon.
- 8Why does the intensity of a beam of electromagnetic radiation decrease with distance from the source?Because the radiation spreads out over a wider and wider area, so the surface area it reaches it ever increasing. Also, it is partially absorbed by the medium it travels through.
- 9What is ionisation?Removing an electron from an atom or molecule, which can initiate chemical reactions.
- 10Which types of electromagnetic radiation are ionising?Ultraviolet, X-Rays, Gamma Rays.
- 11The _______ ________ of absorbed radiation can damage living cells.Heating Effect
- 12What issues do some people have with low-intensity microwave radiation.They think that mobile phones and masts increase health risks because the radiation warms the brain slightly.
- 13Explain how microwaves can be used to heat a potato.A potato contains water, so it absorbs microwave radiation and vibrates, so its temperature rises.
- 14How are microwave users protected from radiation?The oven door has a metal grid to reflect the radiation back inside the oven. It has a switch which prevents the oven from operating with its door open.
- 15What do radioactive materials emit?Ionising gamma radiation all of the time.
- 16What does the ozone layer do?It absorbs ultraviolet radiation, emitted by the Sun, producing chemical changes in that part of the atmosphere.
- 17How does the ozone layer protect living organisms?It absorbs some of the radiation which the sun emits.
- 18How can sun creams and clothing protect people against ultraviolet radiation?They can absorb some of the radiation.
- 19What are the benefits of some physical barriers absorbing some ionising radiation?X-rays are absorbed by dense materials, so the can produce shadow pictures of bones or of aircraft luggage. Radiographers can be protected by wearing dense materials such as lead and concrete.
- 20All objects emit __________ ________ with a _______ ________ that ________ with ________.Electromagnetic Radiation
Principal Frequency
Increases
Temperature - 21The ______ is surrounded by an _______ which......Earth
Atmosphere
Allows some of the electromagnetic radiation emitted by the sun to pass through. - 22What does the electromagnetic radiation do then it is absorbed?It warms the Earth's surface.
- 23Explain the greenhouse effect.The radiation emitted by the Earth, which has a lower principal frequency than that emitted by the Sun, is absorbed or reflected back by gases in the Earth's atmosphere; this keeps the Earth warmer than it would otherwise be.
- 24What are some of the greenhouse gasses in the Earth's atmosphere?Carbon Dioxide
Methane
Water Vapour - 25Why, for thousands of years, was the amount of carbon dioxide in the Earth's atmosphere approximately constant?Plants absorbed carbon dioxide during photosynthesis, then animals and decomposes returned it to the atmosphere during respiration. Humans burned wood, but that was balanced by new trees growing.
- 26Why has the amount of carbon dioxide in the atmosphere been steadily rising over the last two hundred years?Because fossil fuels are being burned in increasing quantities, which releases the carbon dioxide which was stored in them into the atmosphere.
Deforestation releases carbon dioxide and reduces the amount removed by photosynthesis.
Methane is produced by grazing animals and rice paddies. - 27What are computer climate models used for?Providing evidence that human activities are causing global warming.
- 28What could global warming result in?- Inability to grow food crops in particular regions.
- More extreme weather events due to increased convection and larger amounts of water vapour in the hotter atmosphere.
- Flooding of land due to rising sea levels, caused by melting continental ice and thermal expansion of water.
- Malaria will spread if mosquitoes can breed in more areas. - 29Why can electromagnetic radiation of some frequencies be used for transmitting information?- Some radio waves and microwaves are not strongly absorbed by the atmosphere so can be used to carry information for radio and TV programmes.
- Light and infrared can be used to carry information along optical fibres because the radiation travels large distances through glass without being significantly absorbed. - 30How can a signal be created?It can be superimposed on to an electromagnetic carrier wave.
- 31What is an analogue signal?A signal that can vary continuously.
- 32What is a digital signal?A signal that can only take a small number of discrete values (usually two).
- 33How can sound an images be transmitted?As a digital signal.
- 34How can digital information be carried?By switching the electromagnetic carrier wave off and on to create short bursts of waves (pules).
- 35What happens when the waves are received?They are decoded to produce a copy of the original sound wave or image.
- 36What are the advantage of digital signals over analogue signals?If the original signal has been affected by noise it can be recovered more easily because the electronic circuit which removes the noise restores it to its nearest value (0 or 1). this is done through a re-generator.
- 37What is measured in Bytes (B)?The amount of information needed to store an image or sound.
- 38The ______ information stored, the _______ the quality of the sound or image.More
Higher - 39What are the other advantages of digital signals?- They can be processed by microprocessors (Phones and PCs)
- They can be stored in memories that take up little space
- They can carry more information each second than analogue signals
- They can be delivered with no loss of quality.
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- GCSE Physics Karteikarten am GCSE Physics P2 (OCR), erstellt von Usman Rauf am 16/04/2015.
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- Usman Rauf
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- Erstellt von Josh Price · 16 Apr 2015
- Kopiert von Usman Rauf · 16 Apr 2015
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