# P1

At what temperature does water freeze?
0*C
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At what temperature does water boil?
100*C
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What unit is used to measure energy?
Joules (j)
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What happens to the particles when a substance is heated?
As the temperature rises, the particles move faster.
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What does the specific heat capacity mean?
The amount of energy needed to raise the temperature of 1 kg of a substance by 1*C
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Why is water used in central heating systems?
It has a very high specific heat capacity so it can carry large amounts of energy from place to place
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Name some ways to reduce heat loss from a house
Loft insulation, cavity-wall insulation, draught excluder's, thick carpets, double-glazed windows
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What do most insulating methods have in common?
They use air which is a very poor conductor.
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Payback time equation
cost of insulation/annual saving
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What is the frequency of a wave?
The number of waves produced each second
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What do all electromagnetic waves have in common?
They all travel at the same speed in a vacuum
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How does diffraction affect TV reception compared with radio reception?
A house which is hidden from a transmitter behind a hill will receive radio waves more easily than TV waves because the longer radio waves are diffracted round the hill more.
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How does light travel down a flexible optical fibre?
By total internal reflection, over and over again
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What is total internal relfection?
Where light attempts to move from a material like glass into the air and is reflected back into the material it came from without losing any energy.
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What are the properties of laser light?
All of the waves have the same frequency, all of the waves are in phase, the beam is very intense, the beam is very narrow
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How is information stored on a CD?
As a series of pits on a shiny layer beneath the plastic surface
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A laser light reflects from the information layer. The pits cause changes in the phase of the light that can be detected
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Which emits the most radiation: a hot object or a cold object?
A hot object
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Which emits more radiation: a dull black object or a shiny bright object?
A dull, black object
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How is a piece of toast cooked?
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What happens when microwaves interact with water molecules?
They are absorbed and the water heats up
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What happens to microwaves when they interact with plastics or metals?
They are reflected by metals but pass through plastics
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Why are some people concerned about mobile phone masts?
They think that the microwave radiation could be harming their brains because they are absorbing the radiation
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Why are microwaves more dangerous than visible light?
Because you can't see microwaves, and because microwaves can penetrate your body and heat up inner organs.
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How do microwaves cook food?
Microwaves are absorbed by water molecules, which gain thermal energy. The energy is then conducted or convected through the food
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Describe some of the problems with mobile phone signal reception
Diffraction: the microwaves may be diffracted around the edges of buildings or hills. Interference: competing signals may interfere with each other
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What is the difference between a digital signal and an analogue one?
A digital signal only has two levels but an analogue one can have any value.
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They carry much more information because light or infra-red rays have a shorter wavelength. There is no interference between signals.
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What are the advantages of digital signalling?
Improved signal quality (interference can easily be removed). Less need to amplify the signal. Signal can be multiplexed.
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What are the advantages of a wireless communication network?
Available 24/7. No wires (Duh). Portable and convenient.
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What is ghosting?
When two signals are received at slightly different times.
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Why can radio waves travel long distances?
They are reflected by the ionosphere.
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Why are microwaves used to relay signals to and from satellites?
The short wavelength means that there is little diffraction and that the waves can penetrate the ionosphere.
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Name two kinds of seismic waves.
P : primary. S : secondary
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What are the main differences between P and S waves?
P-waves are longitudinal. They can travel through liquid and solid rock. They travel faster than S-waves. S-waves are transverse, and cannot travel through liquid such as the core.
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What devise is used to detect and measure earthquakes?
A seismometer
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How do we know that most of the core is liquid?
After earthquakes, S-waves are not detected at all seismograph stations because they don't travel through liquid
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How can exposure to UV be reduced?
By using sunblock/cream, staying out of the sun, wearing long-sleeved clothing
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Why is darker skin less likely to be damaged by UV rays?
The pigment melanin in the skin cells absorbs the energy, without is being able to reach the living cells.
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Why are the paths of P-waves and S-waves curved?
The waves are refracted because their speed changes as the density changes
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Which chemicals damage the ozone layer?
CFC's
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## Other cards in this set

### Card 2

#### Front

At what temperature does water boil?

100*C

### Card 3

#### Front

What unit is used to measure energy?

### Card 4

#### Front

What happens to the particles when a substance is heated?

### Card 5

#### Front

What does the specific heat capacity mean?