Questão 1
Questão
Choose the sources of light.
Responda
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Lightbulb
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Sun
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Moon
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Fire
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Water
Questão 2
Questão
Light belongs to the electromagnetic spectrum, a family of electromagnetic waves that travel at a speed of 300 000 km/s through space, which is a vacuum.
Questão 3
Questão
What is a 'photon'?
Responda
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A tiny packet of energy that behaves similar to a wave, but also as a stream of particles.
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A picture taken of light.
Questão 4
Questão
The intensity of [blank_start]electromagnetic[blank_end] radiation gets less as you move [blank_start]further[blank_end] away from the source. The intensity of the Sun's radiation decreases further away from it because it is spread over a [blank_start]larger[blank_end] area. This is why planets more distant from the Sun than the Earth are much [blank_start]cooler[blank_end] than our planet. The earth receives more of the Sun's electromagnetic radiation because the intensity of the radiation is [blank_start]greater[blank_end] closer to the Sun.
[blank_start]Intensity[blank_end] = energy transferred per second per m^2.
If you move a torch closer to a surface, its light spreads over a smaller area and becomes [blank_start]brighter[blank_end]. The total energy from the torch each second is the [blank_start]same[blank_end], but the intensity of light on the surface increases. This happens because as the distance [blank_start]doubles[blank_end], the area the energy spreads over increases four-fold, and so the intensity [blank_start]decreases[blank_end] four-fold.
Responda
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electromagnetic
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further
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larger
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cooler
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greater
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Intensity
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brighter
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same
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doubles
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decreases
Questão 5
Questão
X-Rays have a higher frequency than gamma rays.
Questão 6
Questão
Radiation workers increase their risk of exposure to X-rays and [blank_start]gamma[blank_end] rays. They can choose whether to accept this [blank_start]risk[blank_end]. The risk can be monitored using [blank_start]dosimeters[blank_end], allowing problems to be spotted before too much harm is done.
People who have mobile phone [blank_start]masts[blank_end] built near their homes have exposure to [blank_start]microwaves[blank_end] forced upon them. They tend to be less [blank_start]willing[blank_end] to accept any level of risk, and are more likely to [blank_start]overstate[blank_end] possible risks.
Responda
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gamma
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risk
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dosimeters
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masts
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microwaves
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willing
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overstate
Questão 7
Questão
We are surrounded by ionising radiation all the time. The risk to health is very low, but people tend to overstate it. Why?
Responda
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it is unfamiliar to us
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it is invisible and hard to detect
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effects can be long lasting
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people want to deter new projects eg. nuclear power stations
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people are unsure of risks due to lack of education
Questão 8
Questão
Why does a substance warm up when it absorbs radiation?
Responda
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the energy from the absorbed radiation is transferred to thermal (heat) energy
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the radiation excites the particles, generating thermal energy
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Both!
Questão 9
Questão
The risks to living cells from microwaves are very low because microwaves have a low frequency.
Questão 10
Questão 11
Questão
Ozone is produced when oxygen [blank_start]molecules[blank_end] absorb high energy UV radiation and react together. Ozone molecules may split into an oxygen molecule and a free oxygen [blank_start]atom[blank_end] if they absorb low energy UV radiation. In both these reactions, [blank_start]infrared[blank_end] radiation is emitted. Ozone also reacts with nitrogen, hydrogen, chlorine and bromine [blank_start]compounds[blank_end].
The absorption of [blank_start]ultraviolet[blank_end] radiation in the ozone layer reduces the amount of ultraviolet radiation reaching the Earth's [blank_start]surface[blank_end]. It also causes [blank_start]chemical[blank_end] changes in this part of the atmosphere.
Responda
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molecules
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atom
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infrared
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compounds
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ultraviolet
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surface
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chemical
Questão 12
Questão
Using the diagram, explain what the Greenhouse effect is and how it affects the Earth.
Responda
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Click here when done
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Not here
Questão 13
Questão
Which of the following are greenhouse gases?
Responda
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Water Vapour
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Methane
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Carbon Dioxide
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Sulphur Dioxide
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Nitrogen
Questão 14
Questão
What is Global Warming?
Questão 15
Questão
A digital signal is a type of signal that can take one of a small number of fixed (discrete) values. The values change is discrete steps, and cannot take any values in-between.
Questão 16
Questão
Which of these describes an analogue signal?
Responda
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A signal that can take one of a small number of fixed (discrete) values. The values change is discrete steps, and cannot take any values in-between.
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A signal which can vary continuously.
Questão 17
Questão
There are several advantages of sending information using [blank_start]digital[blank_end] signals:
- different types of [blank_start]information[blank_end] can be sent at the same time
- digital signals can be sent more accurately than [blank_start]analogue[blank_end] signals
- digital information can be stored and [blank_start]processed[blank_end] by computers.
- digital signals can only take certain [blank_start]values[blank_end], so it is easy to tell which part of the signal is real and what is [blank_start]noise[blank_end] (unwanted information mixed in with the original signal).
Responda
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noise
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values
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processed
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analogue
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digital
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information