- Created by: nevewhinn
- Created on: 21-12-16 15:43
What is infrared radiation?
The heat energy transfer by electromagnetic waves.
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Do hot or cold objects emit the most infrared radiation in a given time?
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Do both hot and cold objects emit infrared radiation?
Yes. All objects emit infrared radiation.
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Which spectrum does infrared radiation form a part of?
The electromagnetic spectrum.
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Which types of electromagnetic radiation are emitted by the Sun?
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Why is the Earth’s atmosphere said to act like a greenhouse?
Gases in the atmosphere trap infrared radiation from the Earth, keeping the Earth warm, in a similar way that glass keeps a greenhouse warm.
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Name three gases which contribute to the greenhouse effect.
Water vapour, methane and carbon dioxide.
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How is the greenhouse effect linked to rising sea levels?
The greenhouse effect is causing the Earth to become too warm. As a result, the polar ice caps will begin to melt, causing sea levels to rise.
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Which surfaces are the best emitters of radiation?
Dark, matt surfaces.
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Which surfaces are the best reflectors of radiation?
Light, shiny surfaces.
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Which type of blanket which would be best to keep an accident survivor warm.
A light, shiny blanket.
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Why do matt surfaces absorb more radiation than shiny surfaces?
A matt surface has lots of cavities. These trap radiation so that when radiation is reflected from the surface, it may hit the surface again.
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Why do shiny surfaces reflect more radiation than matt surfaces?
Radiation reflected from the shiny surface travels away from the surface.
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What are the three states of matter?
Solid, liquid and gas
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Which two states of matter can flow?
Liquid and gas
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Which state of matter has a fixed shape?
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Which two states of matter have a fixed volume?
Solid and liquid
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Which state of matter has the lowest density?
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How can we get a substance to change from one state to another?
By heating or cooling it
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What happens to water when we boil a kettle?
The water is heated and turns to steam.
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Which state of matter is steam in?
The gaseous state (gas)
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What happens when ‘dry ice’ warms up?
The solid turns into a gas, without going through a liquid phase.
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What is the scientific word used to describe a gas turning into a liquid through cooling?
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Complete the diagram to show the change of state that occurs when a substance is melted.
Solid -> MELTING -> Liquid
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What are solids, liquids and gases all made up of?
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What happens to the particles when the temperature of a substance is increased?
They gain energy and move faster.
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How are the particles arranged in a solid?
The particles are held next to each other in fixed positions.
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Are particles arranged in a fixed position in a solid?
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Are particles in contact in a solid?
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Do particles move randomly in a solid?
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Are particles arranged in a fixed position in a liquid?
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Are particles in contact in a liquid?
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Do particles move randomly in a liquid?
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Are particles arranged in a fixed position in a gas?
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Are particles in contact in a gas?
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Do particles move randomly in a gas?
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What materials make the best conductors?
Metals, especially copper.
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Which is a better conductor, wood or glass?
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Why are materials like wool and fibreglass good insulators?
They contain trapped air between the fibres and this is a good insulator.
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Describe how ‘free electrons’ move around inside a metal.
They move around at random, colliding with each other and the positive ions.
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When a metal rod is heated, what type of energy do free electrons at the hot end gain?
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How do these free electrons then transfer energy from the hot end to the colder end?
They diffuse and collide with other free electrons and ions in the cooler parts of the metal. When they collide, they transfer energy to these electrons and ions, and so energy is transferred from the hot end to the colder end.
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Where are the electrons found in a non-metallic solid?
In the atoms
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How does energy transfer take place in a non-metallic solid?
The atoms vibrate and shake each other.
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How effective is energy transfer in a metal compared to a non-metal?
Energy transfer in a metal is much more effective than in a non-metal.
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What is convection?
Convection is the circulation of a fluid (liquid or gas) caused by heating it.
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When does convection happen?
Whenever we heat a fluid
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What happens to the hot gas around a lit candle?
The hot gases near the flame go straight up.
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In a domestic water system, should a hot water storage tank be placed above or below a boiler?
Above, because when the water is heated, it will rise from the boiler into the storage tank.
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What causes a sea breeze?
The ground heats up faster than the sea, which warms the air above the ground. The air above the ground rises, which draws in cooler air from the sea as a ‘sea breeze’.
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Where can convection take place?
Only in fluids (liquids and gases)
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Why does the density of a fluid decrease when it is heated?
When heated, the particles in a fluid move about more, taking up more space. Therefore, the same mass of fluid takes up a bigger volume, decreasing the density.
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How does heating cause circulation currents?
Where a fluid is heated, it rises, and then falls again where it is cooled. This causes a circulation current.
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What happens to the water on clothes when they are hung out on a washing line?
The water evaporates.
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What can be observed when a saucer of water is left in a well-ventilated room?
The water gradually disappears, until all the water has evaporated.
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What is evaporation?
Evaporation is when a liquid turns into a gas.
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In a steamy bathroom, what happens to water vapour in the air when it hits a mirror?
It cools down and condenses on the mirror.
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What is condensation?
Condensation is when a gas turns into a liquid (the opposite process to evaporation).
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Why might a doctor or nurse use a liquid that easily evaporates to numb your skin before an injection?
As the liquid evaporates, it cools the skin down, making it too cold to feel any pain.
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What kind of forces exist between the molecules in the liquid?
Weak, attractive forces.
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What kind of energy allows the faster molecules to escape from the liquid?
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Why is the liquid cooler after the faster molecules escape?
Because the average kinetic energy of the remaining molecules has decreased.
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Describe three ways to increase the rate of evaporation of a liquid.
1) Increase the surface area of the liquid. 2) Increase the temperature of the liquid. 3) Create a draught across the liquid’s surface.
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Why do clothes on a washing line dry faster if they are in sunlight?
The Sun warms up the water, which speeds up evaporation.
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Why do we usually spread out clothes when we hang them out to dry?
This increases the surface area, which also speeds up evaporation.
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Describe two ways that the rate of condensation can be increased.
1) Increasing the surface area. 2) Reducing the surface temperature.
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In a steamy kitchen, will the rate of condensation be greater on a big or small window pane?
A big window pane, because it has a larger surface area
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Will there be more condensation if the window is warm or cold?
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Why does a car engine need a cooling system?
So that it doesn't overheat.
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How does a fan cool down a hot engine?
By increasing the flow of air over the surface of the radiator
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How does a vacuum between the two walls in a vacuum flask stop a hot drink from cooling down?
By cutting out energy transfer by conduction and convection between the two walls
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What material are the two walls made from?
Glass (or plastic)
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Why is glass used?
Because it is a poor conductor.
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What type of cooling does the cap prevent?
Cooling by evaporation
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Why is the cap made from plastic?
Because plastic is a good insulator, which cuts down energy transfer by conduction
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Will increasing the temperature difference increase or decrease the rate of energy transfer?
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Name three design factors that can change the rate at which an object transfers energy.
1) The shape of the object. 2) The material the object is in contact with. 3) The surface area of the object.
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Why are the big ears of a desert fox better for keeping cool than small ones?
Big ears have a larger surface area than little ears, so they transfer energy to the surroundings more quickly than little ears would.
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When a substance is heated, what three factors determine the temperature rise?
1) The amount of energy supplied. 2) The mass of the substance. 3) What the substance is.
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How does the mass of a substance affect the rate of temperature change?
The rate of temperature change is decreased. (Temperature changes more slowly.)
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What is meant by the ‘specific heat capacity’ of a substance?
The amount of energy needed to raise the temperature of 1 kg of the substance by 1 °C
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Write down the equation you would use to find the specific heat capacity.
c = E / m × θ
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What does the symbol c mean? What is it measured in?
Specific heat capacity, measured in J/kg°C
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What does the symbol E mean? What is it measured in?
Energy transfer, measured in J
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What does the symbol m mean? What is it measured in?
Mass, measured in kg
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What does the symbol ѳ mean? What is it measured in?
Temperature, measured in °C
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What property of the bricks used in storage heaters allows them to store lots of energy?
They have a high specific heat capacity.
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Why do storage heaters use electricity at night?
Electricity is sometimes cheaper at night, and this makes them cheaper to heat.
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Name four ways of reducing the rate of energy transfer at home.
Cavity wall insulation, double-glazed windows, loft insulation and aluminium foil behind radiators.
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What are the types of energy transfer which loft and cavity wall insulation can reduce?
Conduction and convection.
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How does aluminium foil behind a radiator help reduce heat loss in the home?
The foil reflects radiation away from the wall, back into the room.
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What type of energy transfer does the dry air in double-glazed windows help reduce?
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What do U-values tell us?
How much energy per second travels through different materials
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Would an effective insulator have a high or low U-value?
A low U-value
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Which would have a higher U-value: a single-glazed window or a double-glazed window?
A single-glazed window
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Why are solar heating panels usually fitted to a roof that faces south?
So that the panel can make the most of the Sun’s energy
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Give an advantage of installing solar heating panels.
Solar heating panels save money because no fuel is needed to heat the water.
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What is the main disadvantage of installing solar heating panels?
They are expensive to buy and install.
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What is kinetic energy?
The energy of a moving object
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What is elastic potential energy?
The energy stored in a squashed spring
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What is chemical energy?
The energy stored in fuel.
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What is electrical energy?
The energy transferred by an electric current
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What is gravitational potential energy?
The energy of an object due to its position.
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Which main forms of energy are involved when a battery-powered torch is switched on?
1) Chemical energy in the battery. 2) Electrical energy in the wires. 3) Light energy + heat from the bulb
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When an object is dropped, what happens to its gravitational potential energy?
It is transferred to kinetic energy.
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Fill in the energy flow diagram showing the energy transfers that take place when the object is dropped, as it falls and finally as it hits the ground.
Gravitational potential energy -> kinetic energy -> heat and sound energy
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What kind of energy does a rollercoaster gain when it climbs a hill?
Gravitational potential energy
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What happens to the potential energy when the rollercoaster goes over the top of the hill?
It is transferred into other forms of energy as the rollercoaster races downwards.
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What type of energy transfer is caused by air resistance and friction?
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What type of energy does a swinging pendulum have at each of the three points?
1) Gravitational potential energy. 2) Kinetic energy. 3) Gravitational potential energy.
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What important fact does the conservation of energy tell us?
That energy cannot be created or destroyed
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Is there a type of energy transfer that conservation of energy doesn’t apply to?
No, conservation of energy applies to all energy changes.
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During a bungee jump, why doesn’t the bungee jumper bounce back to the same height as the start?
Because some of the initial potential energy has been transferred into its surroundings by heating as the rope stretched then shortened again
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What is ‘useful energy’?
Energy that is transferred to where we want it, in the form we need it
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What do we mean by ‘wasted energy’?
Energy that is not useful energy and is not usefully transferred
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What happens to wasted energy?
It spreads out to the surroundings, heating them up.
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When a car is braking, what force (between the disc pad and the wheel disc) causes the car to slow down?
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Why do the disc pads and the discs heat up?
Some of the kinetic energy of the moving car is transferred to heating the disc pads and the discs
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What eventually happens to the useful energy supplied to the wheels of a car?
The energy is eventually transferred to the road and the surrounding air.
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Does energy become more or less useful after we use it?
It becomes less useful as it gets more and more difficult to use for further energy transfers.
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What is mass measured in?
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What is weight measured in?
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What is energy measured in?
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When you lift a heavy object, what kind of energy does the object gain?
Gravitational potential energy
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Why do your muscles warm up when you lift a heavy object?
Because some of the energy used when trying to lift an object is wasted. This then goes into the muscles as heat energy.
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Complete the word equation for the efficiency of a device.
Efficiency = Useful energy transferred by the device / Total energy supplied to the device (× 100%)
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How is a Sankey diagram shown with the words ‘wasted energy’, ‘input energy’ and ‘useful energy’?
Input energy (left) useful energy (right) wasted energy (bottom)
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Why can’t a machine be more than 100% efficient?
Because we can’t get more energy out of a machine than we put into it
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How can we reduce the energy wasted for a car has a high air resistance, which is wasting energy into the surroundings?
Make the car’s shape more streamlined
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How can we reduce the energy wasted for the electrical resistance of wires in a circuit that are causing the wires to get very hot?
Use wires with low electrical resistance instead
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How can we reduce the energy wasted for friction in the wheel bearings of a go-cart causing the wheel to heat up?
Lubricate the bearings to reduce friction
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How can we reduce the energy wasted for a sound created by a rattling hair dryer transferring energy into the surroundings?
Cut out the noise by tightening loose parts
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Name five uses for everyday electrical appliances.
Heating, lighting, creating images, creating sound, making things move
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What are the main ways that electrical appliances waste energy?
By transferring heat and sound into their surroundings
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How did the invention of the clockwork radio benefit people living in remote areas?
Clockwork radios don’t need an electricity supply or batteries, so people living in remote areas with no electricity or access to replacement batteries can listen to the radio without having to find a replacement battery.
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What energy transfer takes place when a musician sings into a microphone at a rock concert?
Sound energy -> electrical energy -> sound energy
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How would you describe a powerful appliance?
An appliance which transfers energy very quickly
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What does power mean?
The rate of transfer of energy
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Write down an equation that you could use to calculate power.
P = E / T
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What unit do we use to measure power?
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How many watts are there in one megawatt (1 MW)?
1,000,000 (one million)
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What is the power rating for an electric light bulb?
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What is the power rating for a space rocket?
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What is the power rating for a railway engine?
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What is the power rating for an electric cooker?
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When a weightlifter lifts a dumbbell, what kind of energy does the dumbbell gain?
Gravitational potential energy
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Is the useful energy out of an appliance the same as the useful energy transferred by it per second?
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Is he total power in the same as the total energy supplied to it?
No. It is the same as the total energy supplied to it per second.
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Complete the equation, calculating efficiency from the useful power out and total power in.
Efficiency = Useful power out / Total power in (× 100%)
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What two factors does the amount of energy supplied to an appliance depend on?
1) The power supplied to the appliance. 2) How long the appliance is used for.
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What term is used to describe the amount of energy that a 1 kW appliance uses in one hour?
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What does E mean? What is it measured in?
Energy transfer, measured in kWh
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What does P mean? What is it measured in?
Power, measured in kW
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What does t mean? What is it measured in?
Time taken for energy transfer, measured in h.
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What is the name of the device used to measure how much electricity is used in the home?
An electricity meter
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What does it give a reading of?
The number of kilowatt-hours of energy supplied to the house by the mains
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How is the total cost of the electricity used in the home calculated from this reading?
Total cost = Number of kWh used × Cost per kWh
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What does the term ‘cost-effective’ mean?
Getting value for money
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Give an example for capital cost.
Buying / installing equipment
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Give an example for running cost.
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Give an example for environmental cost.
Cost of disposal, carbon taxes
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How can insulating your home save you money?
It reduces fuel bills by reducing energy losses from the home.
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Give two different examples of insulation.
Loft insulation and cavity wall insulation
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What is meant by the ‘payback time’ of insulation?
The amount of time it takes to save the same amount of money that you spent insulting your home
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How do we calculate payback time?
Initial cost = Payback time × Saving per year
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Why has the UK government banned the sale of filament bulbs?
They use a lot more energy than other types of light bulb.
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Low-energy light-emitting diodes are the most efficient type of light bulb. Give two other advantages of using these LED bulbs.
1) They don’t draw very much power. 2) They have a very long lifetime.
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Give a drawback of using LED bulbs.
They are expensive to buy.
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How is steam produced in a power station?
Burning fuel heats water in a boiler.
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What are coal, oil and gas types of?
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Where are they obtained from?
Long-dead biological material
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Give an advantage of gas-fired power stations.
They can be switched on very quickly.
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What kind of power station can biofuels be burned in?
Small-scale, gas-fired power stations
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Name the gas that can be obtained from manure, decaying rubbish and sewerage works.
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Name two advantages of biofuels, compared to fossil fuels.
1) Biofuels are renewable. 2) Using biofuels is a carbon neutral process.
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Give a similarity between the way fossil fuel power stations and nuclear power stations generate electricity.
Energy is used to turn water into steam, which drives a turbine that turns electricity generators.
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Why are natural sources of energy known as ‘renewable energy’?
Because they can never be used up
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Why are natural sources carbon-free to run?
Because no fuel is needed to produce electricity
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What does a wind turbine consist of?
An electricity generator on top of a long, narrow tower
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How does the wind turbine use the force of the wind to generate electricity?
The wind drives the turbine’s blades around and this turns a generator at the top of the tower.
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What happens when the wind speed increases?
The wind turbine generates more power.
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How do waves turn a generator in a wave generator?
The waves move the generator up and down, which creates a rocking motion in the generator.
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How is the electricity generated transferred to the shore?
By a cable from the generator to the shore
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Give two disadvantages of wave power.
1) It can spoil areas of coastline. 2) It can affect the habitats of marine life and birds.
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Why are hydroelectric power stations usually built on hills?
Because they generate electricity using water flowing downhill
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How does a tidal power station work?
By trapping each high tide and using it to turn generators
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What does tidal power have in common with wind power?
They both make use of turbines to drive a generator.
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How is energy transferred to you from the Sun?
By solar radiation
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How do solar cells work?
Generate electricity using the Sun’s energy
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How do solar heating panels work?
Heat water directly using the Sun’s energy
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How much of the energy they absorb do solar cells convert into electrical energy?
Less than 10%.
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Which two applications would solar power be useful for?
1) Generating electricity on a desert island. 2) Powering a calculator.
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How does a solar power tower use mirrors to turn water to steam?
The mirrors reflect sunlight onto a water tank, which heats the water, turning it to steam.
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Where does geothermal energy come from?
Energy released by radioactive substances within the Earth
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How do geothermal power stations convert geothermal energy into electricity?
They pump water down to the hot rocks, which turns the water to steam. The steam is then used to drive turbines in the power station.
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How can ‘ground heat’ be used to heat a building?
Water is pumped underground in pipes and heated. It is then pumped round the building, which heats it.
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Why does national demand for electricity increase suddenly when a popular football game on TV ends?
Because lots of people put the kettle on
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State the problems linked to carbon dioxide released burning fossil fuels.
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State the problems linked to sulphur dioxide released burning fossil fuels.
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About how long could it take to use up the Earth’s oil and gas reserves?
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How could carbon dioxide emissions be prevented from entering the Earth’s atmosphere?
Carbon capture and storage
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Give two disadvantages of nuclear power.
1) Nuclear waste has to be stored for centuries. 2) A nuclear reactor explosion could affect the area for many years.
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Why are wind turbines often unpopular with people living nearby?
Some people don’t like the way they look, while others don’t like the way they sound.
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What disadvantage do tidal barrages and hydroelectric schemes have in common?
They can affect plant and animal life.
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What is the National Grid?
A network of cables and transformers which distribute electricity from power stations to our homes
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Why does the National Grid transmit electricity at a very high voltage?
Because a high voltage reduces power loss, which makes the National Grid more efficient
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What is the role of tall electricity pylons?
They carry the high-voltage cables of the National Grid.
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What are step-up transformers used for?
Increase the voltage of electricity leaving the power station to the National Grid voltage
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What are step-down transformers used for?
Decrease the voltage at local substations for use in homes and offices
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Give three reasons why electricity cables aren’t buried underground.
1) It would be much more expensive than building pylons. 2) It would be difficult to bury cables under rivers and canals. 3) It would be more difficult to repair cables.
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What type of power stations have the longest start-up time?
Nuclear power stations
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What makes renewable energy sources unreliable?
The amount of energy they can generate can change, depending on the conditions.
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Describe conditions that could decrease the effectiveness of wind power.
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Describe conditions that could decrease the effectiveness of solar power?
Night-time or variable sunlight during the day
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Describe conditions that could decrease the effectiveness of hydroelectric power?
Reservoirs running dry
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Describe conditions that could decrease the effectiveness of wave power?
Weak waves on very calm days
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What three types of power station are used to meet base load demand?
Coal, oil and nuclear
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How can we cope with varying demand for electricity?
By generating extra electricity using gas-fired power stations and pumped storage schemes
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How can we make use of renewable energy sources when energy demand is low?
We can use them to store energy in pumped storage schemes.
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Name two ways of using waves.
1) Transferring information. 2) Transferring energy
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What type of waves are microwaves and light waves?
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Give three examples of mechanical waves.
Any three of the following: water waves, sound waves, waves on a spring, waves on a rope, seismic waves.
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Do all electromagnetic waves travel at exactly the same speed through a vacuum?
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In which direction is the vibration in transverse waves?
The direction perpendicular to the direction of energy transfer
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Give two examples of transverse waves.
1) Waves on a string. 2) Electromagnetic waves.
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In which direction is the vibration in longitudinal waves?
Parallel to the direction of energy transfer
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Are mechanical waves examples of transverse or longitudinal waves?
They can be either.
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Why do we need to measure waves?
To find out how much energy or information they carry
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When looking at a snapshot of a wave, how can we measure the amplitude?
By measuring the height of the wave from the middle
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How can we measure the wavelength?
By measuring the distance from one wave crest to the next crest (the length of one complete wave)
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What can we say about a wave which has relatively small amplitude?
It’s not carrying very much energy.
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How would you find the frequency of a wave?
By counting how many wave crests pass a fixed point in 1 second
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What is the unit of frequency?
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What can a ripple tank be used for?
Studying water waves in controlled conditions
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The wave speed can be calculated using its frequency and the wavelength. Write down the equation for this.
Wave speed = Frequency × Wavelength
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What is the symbol for wave speed? What is measured in?
v, measured in m/s.
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What is the symbol for frequency? What is measured in?
f, measured in Hz.
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What is the symbol for wavelength? What is measured in?
λ, measured in m.
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What is meant by the term ‘plane mirror’?
A perfectly flat mirror
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What do you see if you look straight at a plane mirror?
An exact mirror image of yourself
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How is a ray of light reflecting off a plane mirror labelled?
Up arrow angle of reflection (left), normal line (middle), down arrow angle of incidence (right)
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When light is reflected from a plane mirror in this way, can the angle of incidence be greater than the angle of reflection?
No, they are equal.
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When looking at an object’s reflection in a plane mirror, the image appears 1 m behind the mirror. What is the distance between the object and the mirror?
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Is the image formed by a plane mirror real or virtual?
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What is meant by the term ‘laterally inverted’?
Back to front, but not upside down
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Give an example of a real image.
An image on a screen
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What is refraction?
The change of direction of waves when they cross a boundary
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When a ray of light passes into a glass block, how big is the angle of refraction compared to the angle of incidence?
It is smaller.
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When a ray of light travels from glass into air, does its direction change towards or away from the normal?
Away from the normal
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What is the letter used to represent the angle of incidence?
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What is the letter used to represent the angle of refraction?
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How does the refraction of light through a prism split light into colours?
By refracting each colour slightly differently
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What happens when waves move through a gap?
They diffract (spread out).
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If you want to make the waves spread out more, what should you do to the gap?
Make it narrower
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What type of wave is an ultrasonic wave?
A sound wave
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In designing an ultrasonic scanner, why should careful consideration be given to diffraction effects?
If the ultrasonic waves from the transmitter diffract too much, the image won’t be very clear.
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What type of waves are used to carry a TV signal?
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What happens to these waves when they pass a hill?
They diffract a little around it.
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Why do people living in hilly areas often have trouble finding a TV signal?
The radio waves don’t spread out enough around the hill.
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How do you make a sound when you speak?
Your vocal chords vibrate, producing sound waves.
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How do you hear someone else speaking?
When the sound waves reach your ears, they make your eardrums vibrate, and so you hear the sound.
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Are sound waves longitudinal or transverse waves?
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What is the range of frequencies that a young person can usually hear?
Between 20 Hz and 20,000 Hz
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What would you hear if you put a ringing alarm clock into a vacuum?
Nothing from the alarm clock
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What is an echo?
265 of 315
Name two ways of reducing echo in a large hall by altering the walls.
1) Cover the walls in soft fabric. 2) Make the wall surface uneven.
266 of 315
What happens to the speed of sound when you heat the air up?
267 of 315
Why does sound refract upwards from the ground during the day, but downwards at night?
Because, during the day, the air near the ground is warmer than the air higher up.
268 of 315
What happens when you increase the amplitude of a sound wave?
The sound gets louder
269 of 315
How can you change the pitch of a musical note?
By changing the frequency of the sound waves
270 of 315
How does a musical instrument produce a sound?
The instrument and the air inside it vibrate strongly, and so we hear notes of sound from the instrument.
271 of 315
Why are acoustic guitars hollow?
So that when the guitar is played, the air inside the guitar vibrates too
272 of 315
What are electromagnetic waves?
Electric and magnetic disturbances that transfer energy from one place to another
273 of 315
What type of waves in the electromagnetic spectrum have the longest wavelength?
274 of 315
Which electromagnetic wave does a sunbed use?
275 of 315
Which electromagnetic wave does a camera use?
276 of 315
Which electromagnetic wave does a radio use?
277 of 315
Which electromagnetic wave does a heater use?
278 of 315
Which electromagnetic wave does a microwave oven use?
279 of 315
Which electromagnetic wave does an X-ray scanner use?
X-rays and gamma radiation
280 of 315
In symbols, write down the wave speed equation
v = f × λ
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What happens to the energy of a wave as you increase the frequency?
The energy increases.
282 of 315
What type of electromagnetic waves carry the most energy?
283 of 315
What is white light?
Light from the Sun and ordinary lamps. It contains all the colour of the visible spectrum.
284 of 315
Is the wavelength of red light longer or shorter than violet light?
285 of 315
What are the light-sensitive cells in digital cameras called?
286 of 315
What happens when infrared radiation hits the skin? Why might this be dangerous?
The skin absorbs the radiation, and it heats up. This can damage or kill skin cells.
287 of 315
Why do optical fibres use infrared radiation instead of light?
Because infrared radiation is absorbed less in the glass fibres
288 of 315
Give two uses of microwaves in communication systems.
1) They carry satellite signals. 2) They carry mobile phone signals.
289 of 315
Is the frequency of a radio wave higher or lower than a microwave?
290 of 315
Which three types of signals are carried by radio waves?
1) TV. 2) Radio. 3) Mobile phones
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What is a Bluetooth signal?
A radio signal at frequencies of about 2,400 million hertz
292 of 315
Why was Bluetooth set up?
To enable different electronic devices to communicate with each other
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How do we create a radio wave?
By applying an alternating voltage to an aerial
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How do we change the frequency of the radio waves?
By changing the frequency of the alternating current used to produce it
295 of 315
What type of waves do we use to carry satellite TV signals?
296 of 315
What is the main use of radio waves with a very long wavelength?
To transmit national and international radio signals
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Why are they used for this purpose?
Because they have a very long range
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What possible hazards are there when using mobile phones?
The radiation might affect the brain.
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Why does the UK government recommend that the use of mobile phones by children should be limited?
Children have thinner skulls than adults, so their brains might be more affected by the radiation.
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What kind of radiation is used to transmit signals through an optical fibre?
Light and infrared raditation
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Why doesn’t the radiation travelling through an optical cable escape from the sides?
The ray of light bounces off the walls of the cable.
302 of 315
What is the Doppler effect?
The change in wavelength and frequency that is observed when a source of waves is moving
303 of 315
When was the Doppler effect discovered?
304 of 315
What can be seen when a light source is red-shifted?
It appears redder
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What term is used to describe light waves being squashed when a star is moving towards us?
306 of 315
How does red-shift depend on the speed of the object?
The faster the object is moving away from us, the greater the red-shift is.
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Name two discoveries that Edwin Hubble made.
1) Light from distant galaxies is red-shifted. 2) The further the galaxy is away from us, the more the light is red-shifted.
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What does this tell us about the universe?
That it is expanding
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Which two ideas does the Big Bang theory state?
1) The universe is still expanding after exploding suddenly from an initial point. 2) The universe started with the Big Bang creating space, time and matter.
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What type of radiation, evidence for the Big Bang theory, was discovered in 1965?
Cosmic microwave background radiation
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When was the cosmic microwave background radiation (CMBR) created?
Just after the Big Bang
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What type of radiation was the CMBR when it was created?
313 of 315
Why is the CMBR now microwave radiation?
It has stretched out as the universe has expanded.
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What form of energy do scientists think is responsible for the expansion of the universe accelerating?
315 of 315
Other cards in this set
Do hot or cold objects emit the most infrared radiation in a given time?
Do both hot and cold objects emit infrared radiation?
Which spectrum does infrared radiation form a part of?
Which types of electromagnetic radiation are emitted by the Sun?