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1. What type of wave is transverse?
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2. What is the amplitude of a wave?
2. The maximum disturbance caused by the wave.
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3. What is the wavelength?
The distance between corresponding points on two successive disturbances.
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4. What is frequency?
The number of waves produced (or pass a particular point) per second.
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5. What is the electromagnetic spectrum?
A continous spectrum that extends beyond each end of the visable spectrum for light.
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6. What is the order of the electromagnetic waves?
Radiowaves, Microwaves, Infrared, Visible light, ultraviolet, x-rays, gamma.
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7. How do you calculate the speed of a wave?
Wave speed = frequency x wavelength
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8. Remember that all electromagnetic waves, including light travel at the .................. in a ....................
Same speed in a vacumn.
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9. What is reflection?
Change in a direction of a wave at a boundry between two media.
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11. What is refraction?
A change in direction of a light ray as it passes from one medium to another and changes speed.
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12. What is diffraction?
When a wave spreads out as it passes through a gap.
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13. When does maximum diffraction occur?
When the gap is the same size as the wavelength. This limits the resolution and quality of the image produced by telescopes and microscopes.
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14. What is the angle of incidence?
The angle at which they hit the boundry.
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15. What happens if the angle of incidence is below the critical angle (45 degrees).
It is refracted away from the normal.
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16. If the angle incidence is above the critical angle?
Totally internally reflected and not refracted. This is total internal reflection.
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17. What happens if the angle of incidence is equal to the critical angle.
The light travels along the glass-air boundry.
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18. What are optical fibres used for?
To send information in the form of light pulses. Long flexible and has a small diameter. Lighit totally internally reflected.
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19. How does wireless technology work?
19. Electromagnetic waves can be used to send information without optical fibres because it can be relected and refracted in the same way as visiable light.
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20. What are the three main advantages of wireness technology?
Signals are availiable 24 hours a day, no wiring is needed, items can be portable and convenient.
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20. What code was used at the beginning of the last century?
Morse code.
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21. What does morse code use?
Long and short flashes of light to represent letters.
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22. Why does modern technology use visiable light as it's signal?
Light travels very fast.
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23. What is light used for communication produced by?
A laser which is a narrow, intense beam of light.
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24. What are optical fibres used to carry?
Signals in binary code (digital signals).
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25. What are the advantages and disadvantages of light?
A) Travels very fast. Small loss of signal. D) Can not be used for wireless signalling as it doesn't diffract well.
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26. What are the advantages and disadvantages of electrical signals?
A) Can be sent along wires D) The signal deteriorates.
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27. What are the advantages and disadvantages of radio waves as signals?
A) Can be used for wireless signalling as the waves can diffract around obstacles. D) Diffraction leads to signal loss.
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28. What does a laser produce?
A narrow beam of monochromatic (single colour) light.
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29. Lasers produce a beam of light in which all light waves:
Have the same frequency, are in phase with eachother and have low divergence.
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30. What does in phase mean?
All the peaks and troughs match up ie. go up and down together.
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31. Waves in phase transfer ............... of energy.
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32. Waves out of phase transfer ............... overall energy.
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33. What does the amount of radiation (such as infrared) that is absorbed or emitted depend on?
Surface temperature, colour (black is good, white and silver are poor) and texture (dull is good, shiny is poor).
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34. What are microwaves used for?
Heating materials, satallite communication, mobile phones and radar.
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35. What do microwaves do? (eg. How do they heat food etc)
They are absorbed by water and fat molecules, which causes them to heat up. Can penetrate into about 1cm of food. They can cause burns when absorbed by body tissue. And they are reflected by shiny metal surfaces.
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36. What are infrared rays used for?
Heat materials in cooking and in remote controls.
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37. What do infrared rays do? (eg. heat surface of food etc)
They heat the surface of food in cooking. They are reflected off shiny surfaces and are absorbed by black objects.
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38. How do microwaves heat food?
Microwaves are absorbed by the water and fat molecules in the outside layers of the food, increasing kinetic energy of the particles. Energy is then transferred into the centre of the food by conduction or convection.
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39. How do infrared rays heat food?
Infrared rays are absorbed by all the particles on the outside of the food, increasing kinetic energy of the particles. Energy is then transferred to the centre of the food by conduction or convection.
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40. What does the amount of energy a microwave or infrared wave has depend on?
Its frequency.This also determines how dangerous it is going to be.
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41. When are microwaves used to transmit information?
Over large distances that are in line of site.
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42. Why might some areas poor signals? Relate this to mobile phones.
Some areas are not in the line of sight. This is why your mobile phone might cut off or loose signal in certain areas.
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43. Are microwaves in microwave ovens the same wavelength to microwave signals?
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44. Why might microwaves be potientally dangerous and what could be their effects (mobile phones)?
microwaves could cause ear or brain damage tumours, damage or changes to DNA. This could be if you hold your phone up to your ear.
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45. Why are children more at risk from using mobile phones?
Their skulls are very thin.
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46. What do scientists publish studies of?
the effects of microwave radiation from mobile phones and mobile phone transmission masts. This enables other scientists to share their studies and check data from other studies.
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47. Sometimes scientists publish conflicting evidence about studies such as mobile phone safety. In such cases, what must society do?
Make choices by balencing the risks and benefits about their own mobile phone use and/or whether to live near a mobile phone mast.
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48. How can microwaves be lost or affected?
Large obstacles such as trees or mountains, which block the signals. Microwaves are not diffracted around large objects. Poor weather conditions and large areas of surfcse water. The curvature of the earth. Interference between signals.
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49. How are some of these effects reduced?
Limiting distance between transmitters and postioning the masts high on hills and/or tall buildings.
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50. What type of wave is infrared?
An electromatic wave.
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51. Where is infrared used?
Remote controls, automatic door sensors, wireless data for mobile phones or computors, burglar alarms (heat) and security alarms (heat).
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52. How does an infrared signal in a remote control work?
Uses digital codes to control the different functions of the TV. Each function has a different code. When a button is pressed the code is transmitted to the TV as a series of flashes.
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53. What do 0 and 1 mean?
0 means off. 1 means on.
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54. What can analogue signals be used for? Do they vary in amplitude?
Used to transmit data. They do vary in amplitude.
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55. How many values can an analogue signal have within a fixed range of values?
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56. What are amplitude signals similar to?
Sound waves of speech or music.
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57. What can digital signals be used for and how?
Used to transmit data as a series of pulses.
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58. Digital signals dont vary, they only have two states. What are they? Are there any values inbetween?
1 or 0 (on/off). There are no values inbetween.
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59. What does sending two or more digital signals down the same optical fibre at the same time enable? What is this known as?
Enables more information to be sent in one go and is called multiplexing.
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60. What do both digital and analogue signals suffer from?
Interference in the form of noise.
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61. Why doesnt interference affect digital signals?
The signal is only on or off.
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62. What is the quality described as in analogue and digital signals?
Analogue - poor because of interference. Digital - high signal quality as interference is easily removed.
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63. What is radiation used for communication reflected by? And what does this allow?
The atmosphere. This allows broadcasts from the south coast of england to be recieved in france around the curve of the earth.
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64. What do radio stations and other nearby broadcasters transmit using? (frequencies)
Different frequencies to avoid interference.
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65. What is wireless technology used for?
TV, radio broadcasts, mobile phones and laptops (wireless internet).
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66. What are the advantages and disadvantages of using wireless technology?
A) No connection to a phone land-line required. Portable, conveninet and allows access anywhere. D) Aerial is needed to pick up the signal.
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67. What are satallites used for?
Global communication.
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68. How do communications with satallites work?
A signal is sent from a ground station transmitter dish to a satellite receiver dish. A return signal is then sent by the transmitter to a ground receiver dish, which may be in a different country.
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69. What is the ionosphere? Explain abit about it.
An electrically charged layer in the earths upper atmosphere. Longer wavelengths radio waves are reflected by this. This
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70.What can affect communications? (microwaves)
The refraction and diffraction of microwaves.
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71. What does the refraction at the interfaces of different layers in the earth's atmosphere result in?
The waves changing direction.
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72. What does diffraction at the edge of transmission dishes cause?
Causes the waves to spread out, which results in signal loss.
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73. What does interference from similar signals limit?
The distance between transmitters.
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74. What can postioning transmitters in high places help to overcome?
The nuisance of obstacles blocking signals.
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75. What do new DAB radios recieve?
Digital signals
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76. What does DAB stand for?
Digital Audio Broadcasting.
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77. What are most DAB radios also able to recieve?
Old FM radio station signals which are transmitted using anologue signals.
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78. What are the advantages and disadvantages of DAB?
A) More stations availiable. Less interference with broadcasts from other stations. D) Audio quality not as good as FM broadcasts. Some areas cannot recieve DAB .
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79. What do earthquakes produce? And what can these things do? What are they called?
Shock waves. Damage buildings and cause tsunamis. Seismic waves
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80. What can seismic waves be detected by?
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81. What are the two types of seismic wave? And explain their properties.
Primary - longitudinal and travel through both solids and liquids. Secondary - Transverse. Travel through solid but not liquid. They travel slower than P-Waves.
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82. P waves are detected in most places, this means that?
They can travel through the solid crust and mantle and the liquid outer core and inner core.
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83. S waves are only detected closer to the epicentre (centre of the earthquake). This means that?
They can pass through the solid crust and mantle, but they cannot pass through the liquid outer core.
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84. What do seismic waves provide evidence for?
The structure of the earth.
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85. What do many scientists believe we are experiencing in the world?
Global warming.
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86. What three factors contribute to global warming?
Increased energy use in homes or industry. Increased carbon dioxide emissions from fossil fuels. Deforestation (cutting down of large trees).
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87. What natural events can cause change in weather patterns?
Volcanoes (dust reflects radiation from the sun back to space - cooling) Dust from factories reflects radiation from cities back towards earth - warming
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88. What type of waves does the sun produce? What does this cause?
electromagnetic waves causing ultraviolet radation.
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89. What can prolonged exposure to ultraviolet radiation cause?
A tan, sun burn, cataracts, premature ageing and skin cancer.
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90. How can sunscreen be effective?
Reducing the damage caused by ultraviolet radiation.
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91. The higher the ............... the lower the ................. because high factors allow longer exposure without burning.
factor - risk
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92. How long should you spend in the sun without suncreen on in england?
20 minutes.
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93. How many times longer can you stay in the sun if you are wearing factor 30 sunscreen?
30 (factor 30) x 20 (normally 20 minutes) = 600 minutes.
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94. Why do people with darker skin tones have a reduced risk of getting skin cancer?
Skin cancer develops in the delicate tissues below the melanin in the skin. Melanin is the chemical which gives skin its colour. Dark skin absorbs more ultraviolet radiation than light skin. Less ultraviolet radiaition reaches underlying body tissues
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95. What type of media campaigns are used to inform people about the risks of ultraviolet campaigns?
TV adverts. leaflets, newspapers and internet campaigns.
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96. What can you do to reduce the risk of sunburn or skincancer?
Stay out of midday sun, keep skin covered, reduce or avoid use of sun beds and use sunscreen .
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97. What is the ozone?
A gas found high up in the earths atmosphere, it prevents too many ultraviolet rays reaching the earth.
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98. What have scientist noticed recently about the ozone and skin cancer?
There is a link in the decreasing thickness of the ozone and the number of people sufferering from skin cancer.
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99. How do scientists make sure that their study about the ozone is accurate?
Repeat their experiments, consider data from other scientists who relicated their experiments and test their prediction based on current explanations.
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100. How has the discovery of the hole in the ozone layer impacted globally?
Legislation was passed in many countries to ban the use of CFC in fridges, old fridges and freezers containing CFCs must be disposed of and CFCs are no longer used as propellents in aerosol cans. Wider awareness of the risk of UV radiation and cancer
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Card 5


5. What is the electromagnetic spectrum?


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