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Flashcards

p2

blueaweiss Inglês 42 flashcards

Flashcards do conjunto (42)

  1. 1What is the speed of light? (in a vacuum)300 000 km/s
  2. 2Name all the types of radiation in the electromagnetic spectrum going from lowest to highest energy levels?1) Radio waves 2) micro-waves 3) in fared 4) visible light 5) ultra violet 6) X - rays 7) Gamma rays
  3. 3What are photons?Packets of energy with no mass, what make up all electromagnetic radiation
  4. 4List the colours of light from least to most energy?ROYGBIV
    red orange yellow green blue indigo violet
  5. 5How do solar cells work?By absorbing electromagnetic radiation, the solar cell's surface absorbs some of the energy carried by the sunlight and transfers it to electrical energy. The amount of energy depends on the intensity of the radiation.
  6. 6What is intensity the measure of and what does it depend on?Intensity is the measure of energy arriving per second and depends on the number of photons arriving per second and the energy transferred by the individual photons
  7. 7What has more energy red or blue light and why?Blue because the photons carry more energy
  8. 8What happens if a beam of light contains more photons?it is more intense
  9. 9What is the equation for light intensity?intensity = energy transferred per second per metre squared
  10. 10What are ions?charged particles, caused by an atom gaining or losing an electron
  11. 11What is ionisation? and explain how it happensThe forming of a charged happens. When an high energy photon knocks an electron out of an atom creating a positive ion of the atom and a free electron
  12. 12What makes radiation 'ionising radiation' and which electromagnetic radiation is ionising?Having enough energy in the photons to knock an electron out of an atom : high frequency UV, X- rays, gamma rays
  13. 13How is ionisation harmful and why is this?UV can damage skin cells and lead to skin cancer, X-rays can cause cancers to develop, gamma rays can cause cancer and death. The reason it is harmful is the ions produced in ionising radiation still take place in chemical reactions in the body. However these reactions are different compared to before the atom became ionised. Thus processes can go wrong. Damage to the DNA in our cells results can result in mutations which is a starting point for cancer.
  14. 14Why can X rays produce images?They can pass through the skin but are absorbed by the bones.
  15. 15How do people in hospitals reduce their X ray exposure?Leaving the room, standing behind a barrier, wearing a dense apron like a lead apron, wearing a dosimeter ( measure someones exposure to radiation)
  16. 16What are radiographers?People who prepare and analyse X-Ray images as well as treating patines with radiation as needed.
  17. 17Name two things that make people more likely to accept risks?1) they choose it themselves 2) the effects are short term rather than long term
  18. 18What are the 6 main places we are exposed to radiation from and what is the biggest?1) The biggest is Radon gas from the ground 2) gamma rays from the ground and buildings 3) medical sources 4) food and drink 5) cosmic rays 6) nuclear power stations
  19. 19Why is the risk of radiation perceived bigger than it is?It is unfamiliar, it is invisible, the effects are long lasting - cancer
  20. 20What happens when a substance absorbs radiation?It warms up as it absorbs the energy too
  21. 21How do microwave ovens work? And what safety do they have?The microwaves are absorbed by the water. The energy from the microwaves is transferred to thermal energy (the water molecules vibrate and move faster). This heat cooks the food. The are covered in metal casing so the microwaves (which reflect off metal) stay inside the microwave. Also the mesh on the front has holes small enough for micro waves not to be able to get through
  22. 22What is the fear and potential/ real issues with mobile phones and masts?Mobile phones emit very low levels of microwave radiation but we use them so often we have constant exposure, Masts use microwave radiation to communicate with other masts but this is very low intensity at the base of the mast
  23. 23What is Ozone? and why is it good for us?A form of oxygen found it the outer layers of the atmosphere. It is very effective at absorbing UV which can cause sunburn and then cancer. Ozone thus protects living organisms from dangers of UV
  24. 24What happened to the ozone layer?CFC's from fridges caused a whole in the ozone layer
  25. 25What happens in the ozone layer in terms of the reactions?Oxygen molecules absorb high energy UV and react forming Ozone. However if Ozone then absorb low energy UV they may split into and oxygen molecule and a free oxygen atom. In both these reactions infa red is emitted. Ozone also reacts with nitrogen, hydrogen, chlorine and bromine compounds
  26. 26Explain the green house effect?Radiation from the sun reaches earth and is then reflected from the surface back into space. However some radiation reflects off earth and then bounces back off and is re- radiated by the
    gasses in the atmosphere. More greenhouse gasses increases the re radiation and the temperature.
    Most of these gasses responsible for the green house effect is water vapour but some is carbon dioxide and methane. Methane is particularly bad as though there is not that much of it in comparison to other gasses a molecule of methane is contributes 20 times more to the effect than a molecule of carbon dioxide.
  27. 27What is meant by principal frequency?The frequency emitted in the highest intensity by an object. This increases with temperature. It can be seen as colour change for objects hot enough to emit visible light like a hot metal rod.
  28. 28Outline the stages of the carbon cycle?1) plants absorb carbon from the atmosphere 2) animals eat the carbohydrates 3) animals release carbon dioxide during respiration
  29. 29What is global warming?The increase in average temperature worldwide caused by the green house effect.
  30. 30What are scientists concerned about in regards to global warming?Some crops may no longer be able to grow in some regions, the ice caps may melt, sea levels may rise due to this and also as the sea expands if it is warm,
  31. 31What are the causes of extreme weather? and relate it to global warmingA rise in temperature would cause a larger temperature difference between the atmosphere and oceans may increase convection ( the transfer of energy through the atmosphere by circulating masses of air at different temperatures) Warm air holds more water velour meaning more water comes down as precipitation
  32. 32What are computer climate models?Computer models of the climate that allow scientists to make forecasts and predictions and help them to be confident that human activities are causing climate change.
  33. 33How do radio and micro waves travel across the world?Radio waves reflect of a charged layer of the atmosphere and microwaves reflect off satellites
  34. 34How do optical fibres work?They carry in fared waves and light signals by bouncing and reflecting in fared and visible light rays off a glass tube at such an angle they move down the optical fibre
  35. 35How do waves carry information?A carrier wave (which is an electromagnetic wave usually a radio wave) is modulated by a sound or an image, this creates a signal which is transmitted, your receiver like a radio can separate out the modulation from the carrier and play the sound
  36. 36Explain an analogue signal?An analogue signal the carrier signal can vary continuously. Its frequency and amplitude can have any value
  37. 37What are digital signals? And how do they work?A signal that can take one of usually two discrete values. They work by sampling an analogue signal and coding it as a 0 or 1 this creates a string of numbers. This can be transmitted using an electromagnetic carrier wave. The carrier wave is turned on or off creating short bursts called pulses. The value of 1 is a pulse and 0 is no pulse. This is then decoded by a receiver.
  38. 38What are the advantages of digital signals? get 4 for thumbs up1) different types of info can go at the same time like a picture inside a document. 2) more accurate than analogue 3) Can be stored or processed by computers 4) unwanted information called noise can be removed easily from the original signal.Noise is caused by interference with the signal. 5) it is versatile and can be sent between devices
  39. 39Why is noise less of a problem with digital compared to analogue?Digital signals are not effected as even if a 1 or 0 is distorted slightly it is still recognisable as a pulse or no pulse or 0 or 1. Whereas with analogue signals which can take any signal if it is distorted it is not possible to distinguish from the normal signal.
  40. 40What are binary digits and bytes?Binary digits are the strings of 0s and 1s. Each 8 values or make a byte
  41. 41What are pixels? reference high and low quality images and resolution?To store an image the picture is divided into many tiny boxes called pixels. The quality of the picture depends on how many pixels are used. If more pixels are used each one represents a smaller piece of the picture. The number of pixels used is called the resolution
  42. 42How is sound stored and what makes a higher quality?An analogue signal is sampled at regular time intervals. The more samples the higher quality the sound is as it is close to the original as there is information for more parts of it

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Descrição
FlashCards sobre p2, criado por blueaweiss em 09-04-2014.
Criado por
blueaweiss · abr 2014
Atualizado
19 fev 2016
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