P1 Flashcards
(135 cards)
0
Q
How does red-shift support the Big Band thoery?
A
Since we cannot assume that we have a special place in the Universe, this is evidence for a generally expanding universe. It suggests that everything is moving away from everything else.
1
Q
What is all the evidence we have for the big bang theory?
A
The light from other galaxies is red-shifted soThe other galaxies are moving away from us.
The further away a galaxy is, the more its light is red-shifted. The most likely explanation is that the whole universe is expanding. This supports the theory that the start of the universe could have been from a single explosion.
The Cosmic Microwave Background Radiation, CMBR, exists. The relatively uniform background radiation is the remains of energy created just after the Big Bang.
2
Q
What is the big bang theory?
A
The theory states that originally all the matter in the universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion (called the Big Bang), and it is still expanding today.
3
Q
Why does the patterns of lines in the adsorption spectrum for helium move towards the red end of the spectrum when the object is further away?
A
The positions of the lines have changed because of the Doppler effect. Their wavelengths have increased (and their frequencies have decreased).
4
Q
How does red-shift work and what does it show?
A
Astronomers have found that the further from us a star is, the more its light is red-shifted. This is because their wavelengths have increased and their frequencies have decreased. If it was moving closer it would be blue. This tells us that distant galaxies are moving away from us, and that the further away a galaxy is, the faster it’s moving away.
5
Q
How do we know that the sun contains helium?
A
We know this because there are black lines in the spectrum of the light from the Sun where helium has absorbed light. These lines form the absorption spectrum for helium.
6
Q
What is the Doppler effect and how does it work?
A
This effect, where there is a change in frequency and wavelength, is called the Doppler effect.
When a source moves towards an observer, the observed wavelength decreases and the frequency increases giving it a higher pitch.
When a source moves away from an observer, the observed wavelength increases and the frequency decreases giving it a lower pitch.
7
Q
What has been found that supports the big bang theory?
A
Astronomers have even detected a cosmic microwave background radiation, CMBR, that is thought to be the heat left over from the original explosion.
8
Q
What happens when waves meet a medium?
A
The wave speed slows and its wavelength decreases as it passes through the medium. As it reenters the air, the wave speed and wavelength increase back to their original values.
9
Q
What are the uses of gamma radiation?
A
killing cancer cells
10
Q
How do you calculate wave speed?
A
v = f × λ
v is the wave speed in metres per second, m/s
f is the frequency in hertz, Hz
λ (lambda) is the wavelength in metres, m.
11
Q
What are waves?
A
Waves are vibrations that transfer energy from place to place without matter (solid, liquid or gas) being transferred.
12
Q
What are transverse waves?
A
In transverse waves, the oscillations (vibrations) are at right angles to the direction of travel and energy transfer
13
Q
How can radio waves reach receivers that aren’t in view of the transmitter?
A
Diffraction allows low-frequency radio waves to be received behind hills, although repeater stations are often used to improve the quality of the signals. The lowest frequency radio waves are also reflected from an electrically charged layer of the upper atmosphere, called the ionosphere. This means that they can still reach receivers that are not in the line of sight because of the curvature of the Earth’s surface.
14
Q
How do you construct a ray diagram?
A
In a ray diagram, the mirror is drawn a straight line with thick hatchings to show which side has the reflective coating. The light rays are drawn as solid straight lines, each with an arrowhead to show the direction of travel. Light rays that appear to come from behind the mirror are shown as dashed straight lines. Make sure that the incident rays (the solid lines) obey the law of reflection: the angle of incidence equals the angle of reflection. Extend two lines behind the mirror. They cross where the image appears to come from.
15
Q
How can microwaves be used to communicate with satellites?
A
Certain microwave radiation wavelengths pass through the Earth’s atmosphere and can be used to transmit information to and from satellites in orbit. Satellite television signals use microwaves.
16
Q
What is the range of wavelengths in the electromagnetic spectrum?
A
about 10–15 m to more than 104 m.
17
Q
What is the incident?
A
The incoming ray.
18
Q
What waves need to travel through a medium?
A
Sound waves and seismic waves
19
Q
What is the angle of reflection?
A
The angle of reflection is between the reflected ray and the normal.
20
Q
What is the law of reflection?
A
the angle of incidence equals the angle of reflection
21
Q
What do smooth surfaces do when light hits them?
A
Smooth surfaces produce strong echoes when sound waves hit them, and they can act as mirrors when light waves hit them. The waves are reflected uniformly and light can form images The waves can:
appear to come from a point behind the mirror, for example a looking glass
be focused to a point, for example sunlight reflected off a concave telescope mirror.
22
Q
What does the extent of spreading in diffraction depend on?
A
The extent of the spreading depends on how the width of the gap compares to the wavelength of the waves. Significant diffraction only happens when the wavelength is of the same order of magnitude as the gap. For example:
a gap similar to the wavelength causes a lot of spreading with no sharp shadow, eg sound through a doorway
a gap much larger than the wavelength causes little spreading and a sharp shadow, eg light through a doorway.
23
Q
What do rough surfaces do when light hits them?
A
Rough surfaces scatter sound and light in all directions. However, each tiny bit of the surface still follows the rule that the angle of incidence equals the angle of reflection.
24
What happens if the waves cross the boundary of 90 degrees?
Refraction doesn't happen if the waves cross the boundary at an angle of 90° (called the normal) - in that case they carry straight on.
25
What is the image in a plane mirror?
virtual (it cannot be touched or projected onto a screen)
upright (if you stand in front of a mirror, you look the right way up)
laterally inverted (if you stand in front of a mirror, your left side seems to be on the right in the reflection).
26
What is the order of the electromagnetic spectrum from high frequency and short wavelengths, to low frequency and long wavelengths?
```
Granny's Xbox Uses Volts In My Room
Gamma radiation
X-Rays
Ultraviolet
Visible light
Infrared
Microwaves
Radio Waves
```
27
What is the wavelength?
The wavelength of a wave is the distance between a point on one wave and the same point on the next wave.
28
What are the uses of infrared?
optical fibre communication, High intensity infrared is used in heaters, toasters and grills, security lights
burglar alarms. Infrared radiation is also used to transmit information from place to place, including:
Remote controls for television sets and DVD players
data links between computers.
29
What are the uses of radio-waves?
Radio waves are used to transmit television and radio programmes. Television uses higher frequencies than radio.
30
What are the disadvantages of microwaves?
Some people think that mobile phones, which transmit and receive microwaves, may be a health risk. This is not accepted by everyone, as the intensity of the microwaves is too low to damage tissues by heating, and microwaves are not ionising.
31
What is the normal?
The normal is a line drawn at right angles to the reflector (medium)
32
What are longitude waves?
In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer. Longitudinal waves show area of compression and rarefaction.
33
What does visible light require?
The use of visible light needs the transmitter and receiver to be in the line of sight. But it is more secure against eavesdroppers than radio waves.
34
What is the amplitude?
As waves travel, they set up patterns of disturbance. The amplitude of a wave is its maximum disturbance from its undisturbed position. Take care: the amplitude is not the distance between the top and bottom of a wave.
35
What is diffraction?
When waves meet a gap in a barrier, they carry on through the gap. However, the waves spread out to some extent into the area beyond the gap. This is called diffraction.
36
What are sound waves?
Sound waves are longitudinal waves. Their vibrations occur in the same direction as the direction of travel. Sound waves can only travel through a solid, liquid or gas.
37
What are Sounds with frequencies above about 20 kHz called?
Ultrasounds
38
What affects sound and pitch?
the greater the amplitude, the louder the sound
| the greater the frequency, the higher the pitch.
39
What are the uses of microwaves?
cooking, mobile phones
40
What is the medium?
Some waves must travel through a substance. The substance is known as the medium and it can be solid, liquid or gas.
41
What is the frequency and what is its unit?
The frequency of a wave is the number of waves produced by a source each second. It is also the number of waves that pass a certain point each second. The unit of frequency is the hertz (Hz). It is common for kilohertz (kHz), megahertz (MHz) and gigahertz (GHz) to be used when waves have very high frequencies.
42
What is the electromagnetic spectrum?
The electromagnetic spectrum is a continuous range of wavelengths.
43
How can white light be split?
White light can be split up using a prism to form a spectrum. The light waves are refracted as they enter and leave the prism. The shorter the wavelength of the light, the more it is refracted. As a result, red light is refracted the least and violet light is refracted the most, causing the coloured light to spread out to form a spectrum.
44
What are X-rays used for?
To produce medical images of bones
45
What happens if a light ray hits a medium at an angle?
It's speed and direction changes. As the ray enters the medium it is bent towards the normal. The angel of refraction is less than the angle of incidence. When it leaves the medium the ray is bent back into its original direction.
46
What is refraction?
Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction and this effect is called refraction.
47
What are the uses of ultraviolet?
detecting forged bank notes
48
What is the angle of incidence?
The angle of incidence is between the incident (incoming) ray and the normal
49
How can we detect infrared radiation?
We cannot see infrared radiation, but we can feel it as heat energy.
50
What waves don't need to travel through a medium?
Other waves do not need to travel through a substance. They may be able to travel through a medium, but they do not have to. Visible light, infrared rays, microwaves and other types of electromagnetic radiation are like this.
51
How is energy produced in stations the use fossil fuels?
A fuel (such as coal) is used to heat up water into steam, which then turns the turbine which powers the generator which produces electricity.
52
How does wave energy work?
The water in the sea rises and falls because of waves on the surface. Wave machines use the kinetic energy in this movement to drive electricity generators.
53
What are the two main nuclear fuels?
The main nuclear fuels are uranium and plutonium. These are radioactive metals.
54
How do hydroelectric power stations work?
Like tidal barrages, hydroelectric power (HEP) stations use the kinetic energy in moving water. But the water comes from behind a dam built across a river valley. The water high up behind the dam contains gravitational potential energy. This is transferred to kinetic energy as the water rushes down through tubes inside the dam. The moving water drives electrical generators, which may be built inside the dam.
55
How does geothermal energy work in non-volcanic areas?
In some places, the rocks are hot, but no hot water or steam rises to the surface. In this situation, deep wells can be drilled down to the hot rocks and cold water pumped down. The water runs through fractures in the rocks and is heated up. It returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators.
56
What are the disadvantages of wind energy?
Wind farms are noisy and may spoil the view for people living near them. The amount of electricity generated depends on the strength of the wind. If there is no wind, there is no electricity.
57
What is the difference between solar cells and solar panels?
Solar cells are devices that convert light energy directly into electrical energy whilst solar panels use heat energy from the Sun to heat up water.
58
How is wind produced?
The wind is produced as a result of giant convection currents in the Earth's atmosphere, which are driven by heat energy from the sun
59
How does tidal energy work?
Huge amounts of water move in and out of river mouths each day because of the tides. A tidal barrage is a barrier built over a river estuary to make use of the kinetic energy in the moving water. The barrage contains electricity generators, which are driven by the water rushing through tubes in the barrage.
60
How is energy produced from wind energy?
Wind turbines use the wind to drive turbines directly. They have huge blades mounted on a tall tower. The blades are connected to a 'nacelle', or housing, which contains gears linked to a generator. As the wind blows, it transfers some of its kinetic energy to the blades, which turn and drive the generator. Several wind turbines may be grouped together in windy locations to form wind farms.
61
What are the disadvantages of fossil fuels?
Fossil fuels are non-renewable energy resources: their supply is limited and they will eventually run out.
Coal and oil release sulfur dioxide gas when they burn, which causes breathing problems for living creatures and contributes to acid rain.
Fossil fuels release carbon dioxide when they burn, which adds to the greenhouse effect and increases global warming.
62
What are the advantages of wind energy?
Wind is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced.
63
What are the disadvantages of nuclear power stations?
The fuel for nuclear power stations is relatively cheap, but the power stations themselves are expensive to build. It is also very expensive to dismantle old nuclear power stations and to store their radioactive waste, which is a dangerous health hazard.
64
What are the fossil fuels?
The fossil fuels are coal, oil and natural gas. They were formed from the remains of living organisms millions of years ago and they release heat energy when they are burned. They are non-renewable.
65
What are the advantages of water energy?
Water power in its various forms is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced. Tidal barrages and hydroelectric power stations are very reliable and can be easily switched on.
66
What are the advantages of solar energy (solar cells)?
Solar energy is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced. Solar cells provide electricity in remote locations, such as roadside signs.
67
What does it mean if something provides the 'base-load' electricity?
they are run all the time because they take the longest time to start up.
68
Which fossil fuel produces the most carbon dioxide?
Of the three fossil fuels, for a given amount of energy released, coal produces the most carbon dioxide and natural gas produces the least.
69
What are the start-up times of various fuels in order?
1. gas-fired station (shortest start-up time)
2. oil-fired station
3. coal-fired station
4. nuclear power station (longest start-up time).
70
How do power stations work together to provide electricity?
Nuclear power stations and coal-fired power stations usually provide 'base load' electricity - they are run all the time because they take the longest time to start up. Oil-fired and gas-fired power stations are often used to provide extra electricity at peak times, because they take the least time to start up.
71
What are the disadvantages of geothermal energy?
Most parts of the world do not have suitable areas where geothermal energy can be exploited.
72
Where is the voltage changes in the National grid and why?
Power stations produce electricity at 25,000 V. Step-up transformers change the voltage to the very values needed to transmit electricity through the National Grid power lines. Electricity is sent through these at 400,000 V, 275,000 V or 132,000 V. This reduces energy losses during transmission but the voltages would be dangerous in homes. Step-down transformers are used locally to reduce the voltage to safe levels. The voltage of household electricity is about 230 V.
73
What are the advantages of geothermal energy?
Geothermal energy is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced.
74
What are the disadvantages of nuclear fuels?
nuclear fuels are non-renewable energy resources. If there is an accident, large amounts of radioactive material could be released into the environment. In addition, nuclear waste remains radioactive and is hazardous to health for thousands of years. It must be stored safely
75
What is the order of the national grid?
Electricity from a power station goes to:
1. step-up transformers
2. high voltage transmission lines
3. step-down transformers
4. consumers, for example homes, factories and shops.
76
How are transformers used to change the voltage?
Transformers are used in the National Grid. A transformer is an electrical device that changes the voltage of an alternating current (ac) supply, such as the mains electrical supply. A transformer that:
increases the voltage is called a step-up transformer
decreases the voltage is called a step-down transformer.
77
What does it mean if something is a reliable source of electricity?
they can provide power whenever it is needed.
78
Why does the national grid use a low current?
When a current flows through a wire some energy is lost as heat. The higher the current, the more heat is lost. To reduce these losses, the National Grid transmits electricity at a low current. This requires a high voltage.
79
What is carbon capture and how does it work?
Carbon capture and storage is a way to prevent carbon dioxide building up in the atmosphere. It is a rapidly evolving technology that involves separating carbon dioxide from waste gases. The carbon dioxide is then stored underground, for example in old oil fields or gas fields such as those found under the North Sea.
80
What are the disadvantages of water energy?
It has been difficult to scale up the designs for wave machines to produce large amounts of electricity. Tidal barrages destroy the habitat of estuary species, including wading birds. Hydroelectricity dams flood farmland and push people from their homes. The rotting vegetation underwater releases methane, which is a greenhouse gas.
81
How is energy produced from nuclear fuels?
Nuclear fuels are not burnt to release energy. Instead, nuclear fission reactions (where the nuclei in atoms are split) in the fuels release heat energy. The heat energy is then used to boil water. The kinetic energy in the expanding steam spins turbines, which then drive generators to produce electricity.
82
What are the advantages of nuclear fuels?
Unlike fossil fuels, nuclear fuels do not produce carbon dioxide or sulfur dioxide.
83
How does geothermal energy work in volcanic areas?
Several types of rock contain radioactive substances such as uranium. Radioactive decay of these substances releases heat energy, which warms up the rocks. In volcanic areas, the rocks may heat water so that it rises to the surface naturally as hot water and steam. Here the steam can be used to drive turbines and electricity generators.
84
What are the disadvantages of solar energy (solar cells)?
Solar cells are expensive and inefficient, so the cost of their electricity is high. Solar cells do not work at night.
85
What is electrical energy?
energy in moving charges or static electric charges
86
What do electrical meters do?
Electricity meters measure the number of units of electricity used in a home or other building. The more units used, the greater the cost.
87
How do calculate efficiency?
efficiency = (useful energy out ÷ total energy in) × 100 (for a percentage efficiency)
88
Why are Modern energy-saving lamps and LEDs (light-emitting diodes) better than ordinary electric lamps?
Ordinary electric lamps contain a thin metal filament that glows when electricity passes through it. However, most of the electrical energy is transferred as heat energy instead of light energy.Modern energy-saving lamps and LEDs (light-emitting diodes) work in a different way: they transfer a greater proportion of electrical energy as light energy
89
What is the efficiency of a device?
The efficiency of a device is the proportion of the energy supplied that is transferred in useful ways.
90
What are the different forms of energy?
Most Kids Hate Learning GCSE Energy Names.
```
Each capital letter is the first letter in the name of a type of energy:
magnetic
kinetic (movement energy)
heat (thermal energy)
light
gravitational potential
chemical
sound
electrical
elastic potential
nuclear.
```
91
What is nuclear energy?
The energy stored in the nuclei of atoms
92
What is gravitational potential energy?
stored energy in raised objects
93
What happens to energy?
Energy can be transferred usefully, stored or dissipated. It cannot be created or destroyed
94
How do you calculate the cost of electricity?
total cost = number of units × cost per unit
95
What is chemical energy?
stored energy in fuel, foods and batteries
96
What do Sankey diagrams show?
Sankey diagrams summarise all the energy transfers taking place in a process. The thicker the line or arrow, the greater the amount of energy involved.
97
What is elastic potential energy?
stored energy in stretched or squashed objects
98
How is the number of units calculated?
units (kWh) = power (kW) × time (h)
99
How do you calculate the electrical energy transferred by an appliance?
E = P × t
E is the energy transferred in kilowatt-hours, kWh
P is the power in kilowatts, kW
T is the time in hours, h.
```
Note that power is measured in kilowatts here instead of the more usual watts. To convert from W to kW you must divide by 1,000.
Or you can use:
E is the energy transferred in joules, J
P is the power in watts, W
T is the time in seconds, s.
```
100
What do energy transfer diagram show?
Energy transfer diagrams show each type of energy, whether it is stored or not, and the processes taking place as energy is transferred.
101
What are the properties of gases and why?
They flow and completely fill their container-The particles can move quickly in all directions
They can be compressed or squashed- The particles are far apart and have space to move into
102
What is the equation to calculate payback time?
payback time (years) = cost of installation (£) ÷ savings per year in fuel costs (£)
103
How does evaporation occur?
The particles in a liquid have different energies. Some will have enough energy to escape from the liquid and become a gas. The remaining particles in the liquid have a lower average kinetic energy than before, so the liquid cools down as evaporation happens.
104
How do solar powers work?
Solar panels do not generate electricity, but rather they heat up water.Cold water is pumped up to the solar panel where it heats up and is transferred to a storage tank. A pump pushes cold water from the storage tank through pipes in the solar panel. The water is heated by heat energy from the sun and returns to the tank. In some systems, a conventional boiler may be used to increase the temperature of the water.
105
What surfaces are good at absorbing infrared radiation?
dark, matt (dull)
106
When does convection occur?
Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection.
107
What are the adaptions of animals in terms of heat loss?
Elephants have large ears with a large surface area compared to their volume. These allow heat to be transferred from the elephant to its surroundings, helping to keep the animal cool.
In general, similar animals have different ear sizes depending on the climate in which they live. The arctic fox has much smaller ears than the fennec fox, which lives in the desert. The arctic fox must conserve its heat energy in the cold climate, while the fennec fox must avoid overheating in the hot climate.
108
What factors affect the rate at which heat energy is transferred?
The bigger the difference in temperature between an object and its surroundings, the greater the rate at which heat energy is transferred. Other factors also affect the rate at which an object transfers energy by heating. These include the:
surface area and volume of the object
material used to make the object
nature of the surface that the object is touching.
109
How are radiators designed to transfer heat energy?
For example, car radiators are flat, with many small fins to provide a large surface area. Similarly, household radiators are thin and flat, and may have fins so that heat energy is transferred to the room quickly.
110
What causes the rate of evaporation to increase?
the rate of evaporation increases if the temperature of the liquid is increased. It is also increased if:
the surface area of the liquid is increased
air is moving over the surface of the liquid.
111
What surfaces are good at emitting infrared radiation?
dark, matt (dull)
112
How do you calculate specific heat capacity?
Here is the equation relating energy to specific heat capacity:
E = m × c × θ
E is the energy transferred in joules, J
m is the mass of the substances in kg
c is the specific heat capacity in J / kg °C
θ (‘theta’) is the temperature change in degrees Celsius, °C
113
What are the disadvantages of solar energy?
solar panels may only produce very hot water in very sunny climates, and in cooler areas may need to be supplemented with a conventional boiler
although warm water can be produced even on cloudy days, solar panels do not work at night
114
How does condensation occur?
The particles in a gas have different energies. Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down. They come close together and bonds form between them. Energy is released when this happens.
115
What surfaces are bad at absorbing infrared radiation?
Light, shiny
116
How does heat conduction work in metals?
The electrons in piece of metal can leave their atoms and move about in the metal as free electrons. The parts of the metal atoms left behind are now charged metal ions. The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons. These move through the structure of the metal, colliding with ions as they go.
117
What are the arrangements of particles in a liquid?
close together
random
move around each other
118
What is payback time?
The payback time of an energy-saving solution is a measure of how cost-effective it is.
119
What are the arrangements of particles in a solid?
close together
regular pattern
vibrate about a fixed position
120
What is infrared radiation?
Infrared radiation is a type of electromagnetic radiation, which involves waves rather than particles. This means that radiation can even pass through the vacuum of space.
121
How do convection currents happen?
Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.
The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, convection currents that transfer heat from place to place are set up.
122
What are the arrangements of particles in a gas?
far apart
random
move quickly in any direction
123
What are the advantages of solar energy?
solar energy is a renewable energy resource
| no harmful polluting gases are produced.
124
What are the properties of solids and why?
They have a fixed shape and cannot flow- The particles cannot move from place to place
They cannot be compressed or squashed-The particles are close together and have no space to move into
125
What are U-values?
U-values measure how effective a material is an insulator.
126
What does the kinetic theory explain?
explains the properties of the different states of matter. The particles in solids, liquids and gases have different amounts of energy. They are arranged differently and move in different ways.
127
How is heat transferred by conduction?
Heat is applied which causes the particles to become energised and so they vibrate more, and collide with particles next to them, spreading the vibration until the entire solid is vibrating faster and is hot.
128
What is the specific heat capacity?
The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C.
129
What is temperate and what is the units?
temperature is a measure of how hot something is and is measured in °C
130
What is heat and what are the units?
heat is a measure of the thermal energy contained in an object and is measured in J
131
What are the properties of liquids and why?
They flow and take the shape of their container- The particles can move around each other
They cannot be compressed or squashed- The particles are close together and have no space to move into
132
When heat energy is transferred to an object, what does its temperature increase depend on?
the mass of the object
the substance the object is made from
the amount energy transferred to the object.
For a particular object, the more heat energy transferred to it, the greater its temperature increase.
133
What surfaces are bad at emitting infrared radiation?
light, shiny
134
What does it mean if the U-value is low?
The lower the U-value is, the better the material is as a heat insulator.
