Radiation and life

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What is radiation?
Radiation is the continous flow of energy or the transferral of energy
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What are the seven types of radiation that make up the electromagnetic spectrum?
Radiowaves, microwaves, infra-red, visible light, ultraviolet, x rays, gamma rays
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What is a photon?
photons are 'packets' of energy which are emitted from electromagnetic radiation
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What does the amount of energy in a photon depend on?
The frequency of the radiation; gamma rays have the highest frequency as it increases as you go along the spectrum
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What is a source?
A source is an object that emits radiation. For example the sun is a source as it emits infra-red radiation, ultraviolet radiation as well as visible light
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What are the three things that can happen to radiation once it has been emitted from a source?
It can be transmitted- Keep travelling through a medium// It can be refected where it bounces back and finally it can be absorbed
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What are the names of the objects that absorb radiation?
Detectors. For example our eyes are detectors of light
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What does the energy transferred by a beam of photons depend on?
Depends on the total number of photons and the energy of each one. Therefore energy= number of photons x photon energy
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What does the intensity of radiation refer to?
How much energy arrives at a square meter of a surface per scond. It is measured in watts per square metre
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Why does the intensity of radiation decrease with distance from a source?
The beam spread out and also it gets partially absorbed by the medium it travels through
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what are the three types of radiation that can ionise cells and why?
ultraviolet, x rays and gamma rays becuase they have enough photon energy to remove an electron from an atom or a molecule
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Why is ionisation dangerous in the body?
Ionising radiation can damage the dna in cells by causing mutations. This can result in uncontrollable cell division otherwise known as cancer
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What are the benefits of uv radiation?
Provides the skin with vitamin d which is essential in the body, improves mood, prevents seasonal affective disorder and also it allows you to get a sun tan
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What are the risks of UV and how can they be minimised?
Can cause sunburn, skincancer, aging and wrinkles, cataracts. These can be minimised by using protective clothing, sun cream and avoiding the midday sun
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How can radiographers protect themselves from x rays?
They can wear lead aprons which absorb the radiation or stand behind concrete screens to limit the exposure. Longer exposure= more damage
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How do microwave ovens protect the users from microwave radiation?
Microwaves contain metal plates which reflect the waves on to the food, glass screens that absorb the radiation and also metal cases relect the waves to stop them from getting out
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Some people believe that there are risks associated with using microwaves. Why is this?
Some of the radiation is absorbed by your body which causes body tissues to heat up as they contain water. Heating of the brain and jaw can increase the liklihood of having cancer and other medical conditions
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What is the greenhouse effect and why does it occur?
This is where greenhouse gases in the earths atmosphere absorb infra-red radiation emitted from the earth. This traps the heat inside the atmosphere and therefore contributes to global warming.
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How does the O zone layer protect us from UV radiation?
Ozones molecules (o3) absorb uv which splits the molecule into 0 and 02. This raection is reversible.
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What will happen if the amount of ozone in the atmosphere decreases?
More UV radiation will reach earth which can be very harmful to complex organisms like humans due to its ionising properties
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What processes in the carbon cycle remove co2 from the atmosphere?
Green plants remove co2 via photosynthesis. If there are fewer trees the level of carbon dioxide will increase. This is due to food production, population growth and deforestation
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What processes in the carbon cycle return carbon dioxide to the atmosphere?
The respirtaion of plants and animals, respiration of decomposers as they break down dead organic matter and the combustion of fossil fuels and trees.
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What are the consequences of global warming?
Ice caps will melt so seas will expand which will cause flooding, there will also be more extreme weather conditions due to increased convection currents from extra heat and food production will also be affected.
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What are the three types of electromagnetic radiation that can transmit information?
Infra red radiation for tv remote controls, microwaves for mobile phones and satellites and radiowaves for tv and radio transmissions
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Why are radio waves and microwaves good at transmitting information over long distances?
Because they dont get absorbed by the earths atmosphere as much as the other types of radiation with higher frequencies
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How are microwaves used for satellite communication?
A signal from a transmitter is transmitted into space where it is absorbed by a satellite dish. The dish tramits the signal back to a satellite dish on earth which reflects on to a receiver
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How do optical fibres work?
Bounce infra-red and visible light waves off the sides of a thin glass inner core
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Why are infra red and visible light used in optical fibres?
The glass doesnt absorb much of the radiation and therefore the signal doesnt weaken as it travels. This means they can be used to transmit information over long distances.
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What is the difference between a digital and analogue signal?
A digital signal is only made up of two discrete values, 0 and 1, whereas an analogue signal will vary continously and therefore the amplitude and frequency will also vary
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How are digital signals decoded by a reciever?
The signal is made up of 0 and 1s which creates pulses, 0 means no pulse 1 means pulse. The receiver can decode these pulses so create a copy of the original signal
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What is noise and how does it affect digital and analogue signals?
Noise is extra information that a signal picks up when it is transmitted. This changes the amplitude of the signal and makes it difficult to recover which reduces the quality
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What are the advantages of using digital signals over analogue signals?
Digital signals can be regenerated much easier than anaogue signals after noise has disturbed the signal. This makes them have a higher quality and they can be stored and processed by computers
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What is digital infromation stored as and how does it affect the quality of an image?
stored in bytes. The more information stored for an image (larger number of bytes) the higher the quality)
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How can electromagnetic waves be used to carry information?
Have information superimposed on to a carrier wave to create a signal, either digital or analogue
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Other cards in this set

Card 2

Front

What are the seven types of radiation that make up the electromagnetic spectrum?

Back

Radiowaves, microwaves, infra-red, visible light, ultraviolet, x rays, gamma rays

Card 3

Front

What is a photon?

Back

Preview of the front of card 3

Card 4

Front

What does the amount of energy in a photon depend on?

Back

Preview of the front of card 4

Card 5

Front

What is a source?

Back

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