Physics 1a-b Flashcards
1
Q
What is infrared radiation?
A
Emission of electromagnetic waves
2
Q
Where is infrared radiation emitted from?
A
The surface of any object
3
Q
The hotter an object is, more or less radiation is emitted in a given time?
A
The hotter an object is, the more radiation
4
Q
Can you feel infrared radiation?
A
If you stand near something hot like a fire or if you put your hand over the bonnet of a recently parked car
5
Q
What are things called that give out radiation?
A
Emitters
6
Q
What does the amount of radiation depend of?
A
Surface colour and texture
7
Q
What sort of object absorbs and emits more infrared radiation?
A
Dark matt surfaces absorb and emit better than glossy white or silver surfaces at any given temperature
8
Q
Why aren’t light shiny surfaces good at absorbing or emitting infrared radiation?
A
Because they reflect a lot of the radiation and have silver inner surfaces to keep heat in or out depending on whether its storing hot or cold liquid
9
Q
How are solar panels designed?
A
Solar hot water panels contain water pipes under a black surface so that radiation from the sun can be absorbed by the black to heat the water. The heated water can then be used for washing or heating
10
Q
What makes a conductor better?
A
More free electrons and ions being closer together
11
Q
What does kinetic theory describe?
A
How particles move in solids, liquids and gasses
12
Q
What are the three states of matter?
A
Solids e.g. Ice, Liquid e.g. water and Gas e.g. water vapour
13
Q
What are the particles like in solids?
A
Strong forces of attraction hold particles close together, fixed regular arrangement, particles don’t have much energy, can only vibrate about their fixed position
14
Q
What are the particles like in liquids?
A
Weaker forces of attraction between particles, close together but can move past each other, irregular arrangements, more energy than solids so can move in random directions at a low speed
15
Q
What are the particles like in Gases?
A
Almost no force of attraction between particles, have more energy than liquids and solids, free to move and travel in random directions at high speeds
16
Q
What is the definition of conduction?
A
Conduction of heat energy is the process where vibrating particles pass on their extra kinetic energy to neighbouring particles
17
Q
How does a rise in temperature occur with conduction?
A
Some of the extra kinetic energy is passed all the way through the solid, increases the heat radiating from its surface
18
Q
What makes conduction faster?
A
Conduction happens faster in denser solids because the particles are closer together and so will collide more often, therefore pass along more energy
19
Q
What makes a material an insulator?
A
If a material has larger gaps between particles, conduction happens a lot slowly, these are insulators
20
Q
What is an example of a good conductor?
A
Metals because of their free electrons
21
Q
What is the definition of convections?
A
Convection occurs when the more energetic particles move from the hotter region to the cooler region and take their heat energy with them
22
Q
Convection in immersion heaters (1)
A
Heat energy transferred from heater coils to the water by conduction
23
Q
(2)
A
Particles near the coils get more energy so move faster
24
Q
(3)
A
Makes the distance between particles greater, the water expands and becomes less dense
25
(4)
The reduction in density means the hotter water rises above the denser, cooler water
26
(5)
The hot water rising displaces the cooler water forcing it to sink back to the heater coils
27
(6)
The cooler water is then heated and rises creating a convection current as this process repeats. Circulating the heat energy through the water
28
What sort of container is more efficient for convection?
Round or square containers, NOT shallow/wide or tall/thin
29
How does convection work with radiators?
Hot, less dense air by the radiator riser and denser, cooler air sinks and replaces it, convection current occurs
30
What is condensation?
When gas turns to a liquid
31
When does condensation happen?
When a gas cools because the particles slow down and lose kinetic energy, if its cold enough and when the particles are pulled close enough together (attractive forces), it turns to a liquid
32
When does water vapour in the air condense?
When it comes into contact with cold surfaces
33
What is evaporation?
When a liquid turns to gas
34
What temperature can particles evaporate at?
At temperatures that are much lower than the liquids boiling point
35
Particles near the surface of a liquid can escape and become gas particles if...?
If the particles are traveling in the right direction and fast enough to overcome the attractive forces of the other particles in the liquid
36
What happens when the fastest particles evaporate from the liquid?
The average speed and kinetic energy of the remaining particles will decrease
37
What happens when the average speed and kinetic energy decreases?
The liquid cools, the temperature of the remaining liquid falls
38
How can this cooling effect be useful?
Because when you exercise or get really hot, your body cools down as the sweat evaporates
39
What makes the rate of evaporation faster?
Higher temperature so more particles have enough energy to escape, Lower density so the force between particles is lower and they will have more energy to escape, Larger surface area so more particles are able to escape quicker, Greater airflow over the liquid
40
What makes the rate of condensation faster
Lower gas temperature so more particles slow down, Lower temperature of the surface that the gas touches, Higher density so the forces between particles is higher so they cant overcome the forces, Less airflow
41
Where is heat energy radiated from?
From the surface of an object
42
What does the rate of heat energy transfer depend on?
It is faster if there is a bigger surface and more infrared waves being emitted the surface. E.g. radiators have a large surface areas to maximise heat they transfer
43
Why do car and motorbike engines often have 'fins'?
To increase surface area so that heat is transferred away quicker and then engine cools down quicker
44
What are heat sinks?
They are designed to transfer heat away from objects their in contact with such as computer components, they also have fins and a large surface area to make this quicker
45
If two objects have the same surface area but different volumes, which object would cool quicker?
The one with a smaller volume as aa higher proportion of the object will be in contact with its surroundings
46
Some devices are designed to limit heat transfer, what is an example of this?
Vacuum Flasks
47
What are four different parts of vacuum flasks that makes them able to limit heat transfer?
The glass bottle is double walled with a vacuum in between which stops conduction and convection from the sides. Either sides of the walls are silvered to reduce heat loss via radiation. The bottle is supported using insulation foam minimising heat conduction and the stopper is made of plastic filled with cork or foam to reduce and conduction through it
48
How can humans control heat transfer in the winter?
In the cold, hairs on your skin stand up to trap a thicker layer of insulating air around the body, limiting heat loss by convection, some animals do this with their fur
49
How can humans control heat transfer in the summer?
When you get too warm, blood is diverted to flow near the surface of your skin so more heat can be lost by radiation, this is why some people go pink/red when they get too hot
50
What is an example of how animals are adapted for cold climates?
Arctic foxes have small ears so they have a smaller surface area to minimise heat loss by radiation and converse body heat
51
What is an example of how animals are adapted for warm climates?
Desert foxes have large ears so they have a bigger surface area to allow them to lose heat by radiation easily and keep cool
52
How do you work out payback time?
Payback time = initial cost divided by annual saving
53
What are different ways to make a house more energy efficient?
Loft insulation, Hot water tank jacket, Cavity wall insulation, Double glazing and Draught-proofing
54
What are the most effective methods of insulation?
The ones that give you the biggest annual saving
55
What is payback time?
The time it takes for the money you've saved on heating bills to equal the cost of insulation installation
56
The most cost-effective are usually the cheapest methods, what does cost-effective mean?
They have a shorter payback time, meaning the money you save covers what you paid really quickly
57
What is cavity wall insulation?
Foam squirted in a gap between bricks to stop convection currents and radiation across the gap, the air pockets (insulator) and insulating foam help reduce heat loss by conduction
58
What is loft insulation?
A tick layer of fibreglass wool laid out across the loft floor and ceiling and reduces heat loss from the house by conduction and convection
59
What is draught proofing?
Strips of foam and plastic around doors and windows stop draughts of cold air blowing in, reducing heat loss due to convection
60
What is a hot water tank jacket?
Lagging such as fibreglass wool reduce heat loss due to convection
61
How do thick curtains help to make a home more energy efficient?
Big bits of cloth over the windows reduce heat loss by conduction and radiation
62
What do U-Values show?
How fast heat can transfer through a material
63
What does a higher u-value mean?
Heat transfers through the material quickly
64
What is the u-value like on something that is a good insulator?
It would have a lower u-value
65
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
66
What is the specific heat capacity of water?
4200 J/Kg°C
67
What is the formula for specific heat capacity?
E=m x c x θ Remember the triangle incase you need to rearrange the formula
68
What do each of the symbols stand for in the formula for specific heat capacity?
E = energy transferred(J)
M=Mass (kg)
C=Specific heat capacity (J/Kg°C)
θ=Temperature change (°C)
69
Why do heaters have high heat capacities?
To store lots of energy
70
How do heaters have high heat capacities?
The materials used have high specific heat capacities also water is pumped around it which has a high specific heat capacity
71
What do electric storage heater do?
They are designed to store energy at night when electricity is cheaper so it can be released during the day
72
How do electric storage heaters work?
The energy is stored using concrete or bricks as they have a high specific heat capacity
73
Some heaters are filled with oil, why is this not as good as water?
Because oil has a lower specific heat capacity than water although it does have a higher boiling point meaning they can safely reach higher temperatures than water
74
What are the nine types of energy, plus examples?
Electrical - currents
Light - sun, light bulbs
Sound - Speakers
Kinetic/movement - anything moving
Nuclear - nuclear reactions
Thermal/heat - hot objects to cooler ones
Gravitational potential - anything that can fall
Elastic potential - springs, elastic, rubber bands
Chemical - foods, fuels, batteries
75
Elastic potential, gravitational potential and chemical energy are forms of what type of energy?
Stored energy because the energy is not obviously happening, its waiting to happen
76
What is the conservation of energy principle?
Energy can be transferred usefully from one form to another, stored or dissipated - but it can never be created or destroyed
77
What does dissipated mean?
Energy is spread out and lost
78
What is the other principle?
Energy is only useful when it can be converted from one form to another
79
What are examples of energy transfer?
```
Electrical energy (TV) turns to light and sound energy
(Batteries) chemical turns to electrical and heat energy Potential energy turns to kinetic and heat
```
80
What makes a device less efficient?
When transforming energy, some energy is often lost, often as heat, the less energy wasted, the more efficient something is
81
How can you calculate efficiency?
Either: useful energy out ÷ total energy in.........
OR useful power out ÷ total power in
REMEMBER THE TRIANGLE
82
What is the statement for efficiency of devices?
No device is 100% efficient and the wasted energy is usually spread out as heat
83
What is an exception to this rule?
Electric heaters as they are usually 100% effective as all the electrical energy is transformed into useful heat energy
84
When choosing appliances, what two things need to be considered?
Cost effectiveness and efficiency
85
How do you work out payback time?
payback time (years) = cost of installation (£) ÷ savings per year in fuel costs (£)
86
What are heat exchangers and how do they make wasted energy useful again?
They reduce the amount of heat energy that is lost by pumping a cool fluid through escaping heat, the temperature of the fluidises as it gains heat energy, it can then be converted into a form of useful energy again
87
In an energy transformation diagram, what does the thickness of an arrow tell you?
It represents the amount of energy
88
What is the proper name for energy transformation diagrams?
Sankey diagrams
89
What are the units of energy?
Kilowatt-hours (KWH)
90
What is the formula for energy?
Energy = power x time
91
What is energy usually measured in?
Joules (J) eg 1 J is the amount of energy transferred by a 1w appliance in 1s
92
What is a KWH, kilowatt-hour?
The amount of electrical energy used by a 1KW appliance left on for one hour
93
How is heat energy transferred?
Radiation, conduction and convection
93
How is heat energy transferred?
Radiation, conduction and convection
94
What sort of heat transfer is heat radiation?
The transfer of heat energy by infrared radiation
95
What do conduction and convection involve the transfer of?
They involve the transfer of energy by particles
96
What is the main form of het transfer in solids?
Conduction
97
What is the main form of heat transfer in liquids and gasses?
Convection
98
What state of matter can emit infrared radiation?
All. Liquids, solids and gassess
99
What makes energy transfer by heat quicker?
A bigger temperature difference between a body and its surroundings
100
Where can you feel infrared radiation?
If you stand near something hot like a fire or the bonnet of a recently parked car
101
How do you work out efficiency?
Efficiency=useful power/energy out DIVIDED BY total power/energy in
102
What are heat exchangers?
They reduce the amount of heat energy that is lost
103
How do heat exchangers work?
They pump cool fluid through the escaping heat, the temperature of the fluid rises as it gains heat energy. The heat energy can then be converted into another useful form of energy
104
What is an example of waste energy becoming useful again?
Heat from a car's engine can be transferred to the air to heat the passenger compartment
105
What is non renewable energy?
Energy that will run out one day and do damage to the environment but provide most of our energy
106
What are the 4 non renewable energy resources?
The three fossil fuels: coal, oil, natural gas, and nuclear fuels: uranium and plutonium
107
What are renewable energy resources?
Energy sources that will never run out, do damage to the environment (in a less nasty way than non renewable sources) but don't provide much energy as they are unreliable because they depend on weather
108
What are the renewable energy resources?
Wind, waves, tides, hydroelectric, solar, geothermal, food and biofuels
109
How do power stations work?
Fossil fuel is burned to convert its stored chemical energy into heat energy, heat energy is used to heat water or sometimes air (fossil fuel power stations) to produce steam. The steam turns a turbine, changing heat to kinetic energy, Turbine is connected to a generator which transfers the kinetic energy into electrical energy
110
What are nuclear power stations?
The same as a power station but they use nuclear fission or uranium or plutonium to produce the heat to make the steam drive a turbine.
111
What power station has the longest start up time?
Nuclear power stations
112
Which fossil fuel power station has the quickest start up time?
Natural gas power stations
113
What does wind power involve?
Lots of wind turbines put up in exposed places like moors or around coasts
114
How do the wind turbines generate electricity?
Each wind turbine has its own generator inside it, the electricity is generated directly from the wind which turns the blades and then powers the generator
115
What are the advantages of using wind turbines to generate electricity?
They are renewable as the wind wont run out and also there is no pollution except for when they are being manufactured. There are no fuel costs and minimal running costs. Also there is no permanent damage to the landscape, if the turbines are removed, the noise and view returns to normal
116
What are the disadvantages of using wind turbines to generate electricity?
They spoil the view because 1500 wind turbines are needed to replace one coal fired power station. They are noisy which is annoying for people that live near to them. No wind=no power. Cant increase supply when demand increases. Also initial costs are quite high
117
How do solar cells generate electricity?
They generate it from the sunlight so they are the best source of energy for calculators and watches also because they don't use up much electricity
118
Where is solar power often used?
In remote places where there's not much choice eg the Australian outback. And also to power electric road signs and satellites. They are only usually used to generate electricity on a small scale like powering individual houses
119
What are the advantages of using solar cells to generate electricity?
There is no pollution except for when they are manufactured. In sunny places it is a very reliable source of energy but can still be used in cloudy places. Energy is free and running costs are almost nothing.
120
What are the disadvantages of using solar cells to generate electricity?
Can only generate electricity in the day time. Initial costs are high. Often not practical or too expensive to connect them to the national grid as the cost of connecting them can be to big compared to the value of the electricity generated.
121
What does hydroelectric power use?
Falling water so it usually requires the flooding of valleys by building big dams
122
How does hydroelectric power work?
Water is stored and then falls, powering the turbines that power the generator
123
What are the advantages of using hydroelectric power?
It can provide an immediate response to an increased demand for electricity. It is very reliable except for in times of drought. There are no fuel costs and minimal running costs and can be very useful to generate electricity on a small scale in remote areas
124
What are the disadvantages of using hydroelectric power to generate electricity?
There is a big impact on the environment due to the flooding of the valley (rotting vegetation produces methane) also there can be a loss of habitat for some species and the reservoirs look ugly when they dry up and the initial costs are high
125
How do most power stations make sure there is enough energy at night?
They keep the huge boilers running all night even though the demand is very low however this means there is extra energy at night that doesn't get used
126
What is one of the best solutions for storing energy for later use?
Pumped storage systems
127
What is pumped storage?
The spare electricity at night is used to pump water to a higher reservoir which can then be released quickly during times of high demand such as teatime each evening
128
Pumped storage and hydroelectric power use a similar idea but what is the difference?
Hydroelectric power generates energy whereas pumped storage is just a way of storing energy which has already been generated
129
What does wave power consist of?
Lots of small wave powered turbines located around the coast
130
How does wave power generate electricity?
As waves come to the shore they provide an up and down motion which can be used to drive a generator
131
What are the advantages of using wave power?
There is no pollution, no fuel costs and minimal running costs.
132
What are the disadvantages of wave power?
They spoil the view, can be a hazard for boats, they are fairly unreliable as waves tend to die down when the wind drops and it is never likely going to be used on a large scale however it can be very useful on small islands.
133
What are tidal barrages?
Big dams built across river estuaries with wind turbines in them. They use the sun and moon's gravity
134
How do tidal barrages work?
As the tide comes in, it fills up the estuary to a height of several meters and drives the turbines, the water can be allowed through the turbines at a controlled speed.
135
What are the advantages of using tidal barrages?
There is no pollution, tides are quite reliable as they always happen twice a day and are always near their predicted height. Also there are no fuel costs and minimal running costs and has the potential for generating a significant amount of energy. Also they are good for storing energy for times of high demand
136
What are the disadvantages of using tidal barrages?
They prevent free access by boats, spoil the view, alter the habitat of the wildlife, they don't work when the water level us the same either side of the barrages and this happens four times a day. Initial costs are quite high and can only be used in suitable estuaries
137
What is geothermal energy?
Heat from underground
138
Where can geothermal energy be used?
Only in volcanic areas where hot rocks lie quite near to the surface. The source of much of the heat is the slow decay of various radioactive elements, including uranium, deep inside the earth
139
How does geothermal energy work?
Steam and hot water rise to the surface and are used to drive a generator
140
What are the advantages of using geothermal energy?
It is free energy that has no real environmental problems. In some places it can be used to heat a building directly without having to be converted to electrical energy
141
What are the disadvantages of using geothermal energy?
There aren't many suitable locations for the power plants and the cost to build the power plant can be quite high compared to the amount of energy you can get out of it
142
What are biofuels?
Fuels made from plants and waste
143
How are biofuels used to generate energy?
The same way as fossil fuels, they're burnt to heat up water which becomes steam, turns turbines, powers generator etc.
144
How else can biofuels be used?
They can be used to power cars-just like fossil fuels.
145
What is an example of a solid biofuel?
Straw, nutshells and woodchips
146
What is an example of a liquid biofuel?
Ethanol
147
What is an example of a biofuel gas?
Methane 'biogas' from sludge disasters
148
Where can we get biofuels from?
Organisms that are still alive or from dead organic matter like fossil fuels but from organisms that have been living much more recently eg crops like sugar cane can be fermented to produce ethanol, or plant oils can be modified to produce biodiesel
149
What do all three fossil fuel release when they are burned?
They release CO2 into the atmosphere. For the same amount of energy produced, coal releases the most CO2 followed by oil, then gas.
150
What is bad about CO2 being released into the atmosphere?
It all adds to the greenhouse effect and contributes to global warming
151
What else is released when coal and oil are burned?
Sulfur dioxide which causes acid rain-it can be harmful to trees and soils and can have far-reaching effects in ecosystems.
152
How can acid rain be reduced?
By taking the sulfur out before the fuel is burned, or cleaning up the emissions
153
Why isn't coal mining good for the environment?
It messes up the landscape, especially open-cast mining
154
Why isn't oil good for the environment?
Because oil spillages can happen and they cause serious environmental problems affecting mammals and birds that live in and around the sea. Even though we try to avoid them, they still happen
155
What are the advantages and disadvantages of nucleur power?
It is clean but the nuclear waste is very dangerous and difficult to dispose of. The fuel is relatively cheap but the overall cost of the power is high due to the cost of the power plant and final decommissioning. Also nuclear power carries the risk of a major catastrophe like the chernobyl disaster in 1986
156
What are the advantages of biofuels?
They are quick and natural source of energy, supposedly carbon neutral.
157
How are biofuels carbon neutral?
The plants that grew to produce the waste absorbed carbon dioxide from the atmosphere as they were growing. When the waste is burnt this CO2 is rereleased into the atmosphere so it has a neutral effect on the atmosphere CO2 levels
158
Why is it hard to keep biofuels carbon neutral?
Because you have to keep growing plants at the same rate as you are burning things
159
What does carbon capture do?
It can reduce the impact of carbon dioxide building up in the atmosphere and reduce the strength of the greenhouse
160
How does carbon capture/storage work?
It collects the CO2 from power stations before it is released into the atmosphere.
161
Where does the captured carbon?
It can be pumped into empty gas fields and oil fields like those under north sea, it can be safely stored without adding to the greenhouse effect
162
What are the ideas developing for new ways to store the captured carbon?
Storing dissolved CO2 in seawater at the bottom of the ocean and capturing CO2 with algae which can then be used to produce oil that can become a biofuel
163
Why are a lot if coal and oil fired power stations being taken out of use?
Because coal and oil are running out
164
What are these power stations being replaced with?
Gas fired power stations because they're quick to get up and there's still quite a lot of gas left/it doesn't pollute as badly as coal and oil
165
What are the factors that have to be considered when building a new power station?
Set up costs, set up/decommissioning time, reliability issues, running/fuel costs, environmental issues and location issues
166
What points are taken into consideration when thinking about set up costs?
Renewable resources often need bigger power stations than non-renewable ones for the same output and bigger power stations are more expensive. Nuclear stations and hydroelectric dams also need huge amounts of engineering to make them safe which increases the price
167
What points are taken into consideration when thinking about set up/decommissioning time?
These are affected by the size of the power station, the complexity of the engineering and also the planning issues. Gas is one of the quickest to set up. Nuclear power stations take the longest, and cost the most, to decommission
168
What points are taken into consideration when thinking about reliability issues?
All non-renewable energy sources are reliable until they run out. Many of the renewable energy sources depend on the wether which means they're pretty unreliable in the uk. The exceptions are tidal power and geothermal which don't depend on the weather
169
What points are taken into consideration when thinking about running/fuel costs?
Renewable energy sources usually have the lowest running because there's no actual fuel involved
170
What points are taken into consideration when thinking about environmental issues?
If theres a fuel involved, there'll be waste pollution and you'll be using up resources. If it relies on weather its often got to be in an exposed place where it sticks out obviously
171
What energy sources cause atmospheric pollution?
Mainly coal, oil and gas
172
What energy sources cause visual pollution?
Coal, oil, gas, nuclear, tidal, waves, wind and hydroelectric
173
What energy sources use up resources?
Coal, oil, gas and nuclear
174
What energy sources cause noise pollution?
Coal, oil, gas, nuclear and wind
175
What energy sources disrupt habitats?
Hydroelectric, tidal and biofuels
176
What energy sources cause the disruption of leisure activities eg boats?
Waves and tidal
177
What energy sources cause other problems?
Nuclear (dangerous waste, explosions, contamination) and hydroelectric (dams bursting)
178
What points are taken into consideration when thinking about location issues?
A power station has to be near to the things it runs on
179
Where are solar panels located?
Anywhere but they're better if theres more sun
180
Where are gas power station located?
Anywhere there's piped fas which is most of the uk
181
Where are hydroelectric dams located?
Hilly, rainy places with floodable valleys eg the lake district/Scottish highlands
182
Where wind turbines located?
Exposed, windy places like moors and coasts or out at sea
183
Where are oil power stations located?
Near the coast as oil is transported by sea
184
Where are wave power located?
On the coast
185
Where are coal power stations located?
Near coal mines
186
Where are nuclear power stations located?
Away from people in case of disaster and near water for cooling
187
Where are tidal power located?
Big river estuaries where a dam can be built
188
Where is geothermal power located?
Fairly limited places, only in places where hot rocks are near the earths surface
189
How is electricity distributed?
Via the national grid
190
What does the national grid do?
Takes electrical energy from power stations to where it's needed in homes and industry. It enables power to be generates anywhere on the grid, and then be supplied anywhere else on the grid
191
What do you need to transmit the huge amount of power needed?
Either a high voltage or a high current
192
What is the problem with a high current?
You lose loads of energy through heat in the cables
193
What is it much cheaper to do?
Boost the voltage up really high (to 400 000 V) and keep the current very low
194
How do you get the voltage to 400 000 V to transmit power?
Using transformers and big pylons with huge insulators but its still cheaper than having a high current and losing loads of energy
195
Why do transformers have to step the voltage up at one end and then bring it back down at the other end?
The voltage is stepped up for efficient transmission and stepped down so its at a safe, usable level
196
What steps up/down the voltage?
Step-up transformers and step-up transformers
197
What are the different electricity can be moved around?
Cables buried in the ground and overhead power lines
198
What the advantages of overhead cables?
Low set up cost, faults are easy to access, easy to set up and there is only minimal disturbance to the land
199
What are the disadvantages of overhead cables?
Lots of maintenance needed, looks ugly, affected by weather and they are less reliable than other cables
200
What are the advantages of underground cables?
Minimal maintenance needed, they are hidden(not ugly), not affected by the weather and more reliable than other cables
201
What are the disadvantages of underground cabled?
High setup cost, faults are hard to access, hard to set up and there is a lot of disturbance to the land
202
Why, in the future, will the energy supplied by the national grid need to increase?
Our energy needs keep on increasing (or our needs will have to decrease so the national grid can stay the same)
203
How cab the energy supply be increased in the future?
Opening more power plants or increasing their power output (or both)
204
How can energy demand be reduced?
Customers using more energy-efficient appliances and by being more careful not to waste energy in the home eg turing lights off, or running washing machines at cooler temperatures)
205
What three things to waves have?
Amplitude, wavelength and frequency
206
What is amplitude?
The displacement from the rest position to the crest (middle line to the top/middle line to the bottom)
207
What is wavelength?
The length of a full cycle of the wave eg from crest to crest
208
What is frequency?
The number of complete waves passing a certain point per second OR the number of waves produced by a source each second
209
What is frequency measured in?
Hertz - Hz is 1 wave per second
210
What are the vibrations like in transverse waves?
Sideways
211
Most waves are transverse ,eg...?
Light (EM Waves), Ripples on water, waves on strings and a slinky spring wiggled up and down
212
What is the definition for transverse waves?
In transverse waves the vibrations are perpendicular (at 90*C) tot he direction of energy transfers of the wave
213
What are the vibrations like in longitudinal waves?
Vibrations along the same line
214
What are examples of longitudinal waves?
Sound waves/ultrasound, shock waves eg seismic waves and a slinky spring when you push the end
215
What are water waves, shock waves and waves in springs and ropes all examples of?
Mechanical waves
216
What is the definition of longitudinal waves?
In longitudinal waves the vibrations are parallel to the direction of energy transfer of the wave
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How do you work out the wave speed?
Wave speed=Frequency x Wavelength
(m/s=Hz x m)
(v=f x λ)
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What would the triangle for this look like?
V over f x λ
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All waves can do what three things?
Be reflected, refracted and diffracted
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Why are waves reflected, refracted and diffracted?
When waves get to an obstacle or meet a new material, their direction of travel can be changed by either reflection, refraction or diffraction
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What does reflection let us do?
See things because light bounces bounces off things (is reflected), into our eyes
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How does reflection let us see things?
When light travelling in the same direction reflects from an uneven surface such as a piece of paper the light reflects off at different angles
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How can reflection let us a reflection?
When light travelling in the same direction reflects from an even surface (smooth and shiny like a mirror) then it's reflected at the same angle and you get a clear reflection
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What is the normal?
An imaginary line that's perpendicular to the surface at the point of incidence
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What is the law of reflection?
Angle of incidence=Angle of relection
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What do you have to do when drawing a ray diagram?
The image the same size as the object, it is as far behind as the object is in front, the image is virtual and upright (virtual as its behind the mirror), the image is laterally inverted (left and right sides are swapped)
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What is refraction?
When waves go through a new material, they change direction
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WHat is diffraction?
When a wave 'bends round' obstacles, causing the waves to spread out when they pass through a gap or pass an obstacle
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What does the amount of diffraction depend on?
The size of the gap relative to the wavelength of the waves, the narrower the gap/longer wavelength, the more the wave spreads out
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How can you tell if the gap is narrow?
If the gap is the same order of magnitude as the wavelength of the wave (they're about the same size)
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Can light be diffracted?
Light has a very small wavelength so for it to diffract, there has to be a really small gap
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What is refraction?
When a wave changes direction because it's speed changes because it crosses the boundary between two different substances
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When are waves refracted?
Only if they meet a new medium at an angle
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What happens if the waves are traveling along the normal but change substance?
They change speed but not direction
235
Why do EM waves have different properties?
Because they have different wavelengths/frequencies in a continuos spectrum
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EM waves vary in wavelength from around what to what?
10 to the power of minus 15 meters to more than 10 to the power of 4 meters
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What are the speeds of the electromagnetic waves?
They all have a speed of 3 X 10 to the power of 8 meters per second, in a vacuum
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What does a higher frequency mean about the wavelength?
A shorter wavelength
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What is the order of the EM waves in the spectrum?
Radio waves, micro waves, infrared radiation, visible light, ultraviolet, X-rays, gamma rays
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What are radio waves mainly used for?
Communication
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What wavelength do radio waves have?
Longer than about 10cm
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How can long radio waves be transmitted from London and received halfway around the world?
Because long wavelengths can diffract around the curved surface of the earth
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What does the diffraction effect make possible for radio signals?
It makes it possible for radio signals to be received even if the receiver isn't in line of sight of the transmitter eg round a hill, into a tunnel
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What is the wavelength like for radio waves used for TV and FM radio?
Very short and the signal doesn't bend. To get reception you have to be in direct sigh of the transmitter but they can be reflected and still received at long distances
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What are microwaves mainly used for?
Satellite communication (TV) and mobile phones
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How does satellite TV work?
Signal from transmitter is transmitted into space where it is picked up by the satellites receiver dish orbiting thousands of kilometres above Earth. The satellite transmits the signal back to Earth in a different direction where it is received by a smaller satellite dish on the ground
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Why do some people think that using your phone a lot or living near a mast is bad for your health?
Because some wavelengths are absorbed by water molecules and heat them up. If the water is your cells then you might start to cook
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Microwaves are used by remote-sensing satellites, what are they?
They can see through clouds and monitor oil spills, track the movement of icebergs and see how much rainforest has been chopped down etc
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What are infrared waves usually used for?
Remote controls and optical fibres
250
How do remote controls work?
By emitting different patterns of infrared waves to send different commands to an appliance eg a TV
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What do optical fibres do?
They carry data over long distances very quickly eg those used in phone lines
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Apart from infrared waves, what other waves do remote controls and optical fibres use?
Visible light
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How do optical fibres work?
The signal is carried out as pulses of light or infrared radiation and is reflected off the sides of a very narrow core from one end of the fibre to another
254
What is visible light useful for?
Photography
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How do cameras work?
They use a lens to focus visible light onto a light-sensitive film or electronic sensor
256
What does the lens aperture control?
How much light enters the camers
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What does the shutter speed determine?
How long the film or sensor is exposed to the light
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How can a photographer capture as much or as little light as they want in their photograph?
By varying the aperture and shutter speed
259
What causes sound waves?
Vibrating objects-the mechanical vibrations are passed through the surrounding medium as a series of compressions
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What type of waves are sound waves?
Longitudinal waves
261
What state of matter does sound travel faster in?
Faster in solids than liquids and faster in liquids than in gasses
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Can sound travel in space?
No because space is a vacuum-there are no particles
263
What happens when sound waves hit hard flat surfaces?
They are reflected
264
Why does an empty room sound different to when furniture is added?
The furniture in the room absorb the sound quickly and stop echoes-echoes are just reflected sound waves
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Why do you hear a delay between the original noise and the echo?
Because the echoed waves have to travel further and so they take longer to reach your ears
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Sound waves also refract when entering different media-they speed up in denser material- why is this hard to notice normally?
Sound waves are always spreading out a lot
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What happens to the pitch when the frequency increases?
It increases-the higher the frequency, the higher the pitch
268
What are common units of frequency?
KHz and MHz
269
What does the loudness of a sound depend on?
The amplitude of the sound wave, the bigger the amplitude, the louder the wave
270
The universe seems to be expanding, what is evidence for this?
Light from other galaxies is redshifted
271
What happens normally when red shift isn't occurring?
Different chemical elements absorb different frequencies of light. Each element produces a specific pattern of dark lines at the frequencies that it absorbs in the visible spectrum
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What happens when we look at light from distant galaxies?
The same patterns but at slightly lower frequencies than they should be-they're shifted towards the red end of the spectrum- redshift
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What is the doppler effect?
The same idea as redshift. The engine sounds lower-pitched when the car's gone past you and is moving away from you. The wavelengths and frequencies seem different to when the source of the wave is stationary
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What will the frequency seem like when the object is moving towards you?
It will seem higher and the wavelength will seem shorter
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What will the frequency seem like when an object is moving away from you?
Lower and its wavelength will seem longer
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When does the doppler effect happen?
In longitudinal waves eg sound and transverse waves eg light
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What happens to the redshift, the further away the galaxy is?
The further away the galaxy is, the greater the red-shift
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What do the measurements of red shift suggest?
All the galaxies are moving away from us very quickly
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How can we estimate the universes age?
It all started with a big bang and everything is still expanding so the age can be estimated by using the current rate of expansion. Estimate is 14 billion years
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What is another theory for the origin of the universe?
The steady state theory, the universe has been and always will be the same. It never started and will never end. Matter is being created in the spaces as the universe expands
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What is the problem with the steady state theory?
The discovery of the cosmic microwave background radiation some years later was strong evidence that the big bang theory was more likely true
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What have scientists detected coming from all parts of the universe?
Low frequency electromagnetic radiation
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What part of the EM spectrum is this radiation mainly?
Microwaves, it is called the cosmic microwave background radiation (CMBR)
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What is the only theory of the origin of the universe that also explains the CMBR?
The big bang theory
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How does the big bang theory explain the CMBR?
After the big bang the universe was extremely hot, everything emitted very high frequency radiation. As the universe expanded, it cooled and the radiation had dropped in frequency and is now seen as microwave radiation
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Why does the big bang theory have limitations?
There are things it cant explain eg it predicts that the universes expansion should be slowing down but its actually speeding up. It explains the expansion but not what caused it in the first place/the conditions before the explosion.
