Physics
AQA P1
Infrared
Radiation
Kinetic Theory
Energy
Transfer by
Heating
Heating and
Insulating
Buildings
Energy
Transfers and
Efficiency
Transferring
Electrical
Energy
Generating
Electricity
The National
Grid
Waves
Sound
Red Shift and
the Big Bang
Theory
Reflection
Infrared Radiation
a) All objects emit and absorb infrared radiation.
b) The hotter an object is the more infrared radiation it radiates in a
given time.
c) Dark, matt surfaces are good absorbers and good emitters of
infrared radiation.
d) Light, shiny surfaces are poor absorbers and poor emitters of
infrared radiation.
e) Light, shiny surfaces are good reflectors of infrared radiation.
Infrared radiation can
be detected. Uses?
Emitting Infrared Radiation
All objects emit (give out) some thermal radiation.
Certain surfaces are better at emitting thermal radiation than
others.
worst emitter
best emitter
matt
black
white
silver
Matt black surfaces are the best emitters of radiation.
Shiny surfaces are the worst emitters of radiation.
Which type of kettle would cool down faster:
a black kettle or a shiny metallic kettle?
Absorbing Infrared Radiation
Infrared waves heat objects that absorb (take in) them.
worst emitter
best emitter
matt
black
best absorber
white
silver
worst absorber
Matt black surfaces are the best absorbers of radiation.
Shiny surfaces are the worst emitters because
they reflect most of the radiation away.
Why are solar panels that are used for heating
water covered in a black outer layer?
Application Questions
Why are marathon runners
wrapped in foil after a race?
Why would dressing like these
ninjas be a bad idea on a
sunny day?
Which t shirt would dry
quickest on washing line?
Why?
Exam Question
Kinetic Theory
a) The use of kinetic theory to explain the different states of
matter.
b) The particles of solids, liquids and gases have different amounts
of energy.
Kinetic Theory
As you heat a substance, the heat energy is transferred to the particles
in the substance as kinetic energy.
This causes the particles to move further apart, decreasing the density
of the substance.
Kinetic Theory
A loss of heat energy will cause the opposite effect.
Application Questions
1. Hot air balloons rise
because a fuel is
burned releasing heat.
Using the kinetic
theory, explain why the
balloon rises.
2. (a) When carbon dioxide is
turned from a gas to a solid,
what two phases happen?
(b)Does this require an input
of thermal energy, or a removal
of thermal energy?
Kinetic Theory – Exam Questions
Energy Transfer by Heating
a) The transfer of energy by conduction, convection, evaporation
and condensation involves particles, and how this transfer takes
place.
b) The factors that affect the rate of evaporation and condensation.
c) The rate at which an object transfers energy by heating depends
on:
• surface area and volume
• the material from which the object is made
• the nature of the surface with which the object is in contact.
d) The bigger the temperature difference between an object and its
surroundings, the faster the rate at which energy is transferred by
heating.
Energy Transfer by Heating
solid
liquid
gas
Particles that are very close together can transfer heat energy
as they vibrate. This type of heat transfer is called conduction.
Conduction is the method of heat transfer in solids but not
liquids and gases.
Energy Transfer by Heating
Warmer regions of a fluid are
more dense than cooler regions
of the same fluid.
The warmer regions will rise
because they are more dense.
The cooler regions will sink as
they are less dense.
This is how heat transfer
takes place in fluids and is called
convection.
The steady flow between the
warm and cool sections of a
fluid, such as air or water, is
called a convection current.
Energy Transfer by Heating
The Earth is warmed by heat energy from the Sun.
How does this heat energy travel from the Sun to the Earth?
infrared
waves
There are no particles
between the Sun and the
Earth, so the heat cannot
travel by conduction or by
convection.
The heat travels to Earth by
infrared waves. These are
similar to light waves and are
able to travel through empty
space.
Energy Transfer by Heating
How is a vacuum flask able to keep hot
drinks hot and cold drinks cold?
2. The plastic (or cork) lid is an
insulator and the screw top
prevents convection currents
escaping from the flask.
1. There is a vacuum between
two layers of glass or steel,
which prevents heat leaving or
entering by conduction.
3. The walls have silvery surfaces,
which prevent heat leaving or
entering by radiation.
Energy Transfer by Heating
Heat loss through evaporation.
Energy Transfer by Heating – Quick Quiz
Energy Transfer by Heating – Exam Questions
Energy Transfer by Heating – Exam Questions
Heating and Insulating Buildings
a) U-values measure how effective a material is as an insulator.
b) The lower the U-value, the better the material is as an insulator.
c) Solar panels may contain water that is heated by radiation from
the Sun. This water may then be used to heat buildings or provide
domestic hot water.
d) The specific heat capacity of a substance is the amount of
energy required to change the
temperature of one kilogram of the substance by one degree
Celsius.
Energy transferred = mass x specific heat capacity x temperature change
Heating and Insulating Buildings
A thermogram shows the distribution of heat over the surface of a
house. It highlights where heat is being lost.
The white, yellow and
red areas are the warmest, so
these are the worst insulated
parts of the house.
The blue and green areas
are the coolest, so these are
the best insulated parts of
the house.
Heating and Insulating Buildings
Heating and Insulating Buildings
The specific heat capacity of a material is the amount of energy
required to raise 1 kg of the material by 1 °C.
It can be used to work out how much energy is needed to raise the
temperature of a material by a certain amount:
energy
= mass
x
specific heat
capacity
Energy is measured in joules (J).
Mass is measured in kilograms (kg).
Temperature change is measured in °C.
Specific heat capacity is measured in J/kg°C.
x
temperature
change
Heating and Insulating Buildings
Using the specific heat capacity of water (4200
J/kg°C), how much energy is needed to increase the
temperature of 600 g of water by 80°C in a kettle?
Note: mass = 600 g = 0.6 kg
energy
= mass x
specific heat
temperature
x
capacity
change
energy = 0.6 x 4200 x 80
= 201 600 J
Heating and Insulating Buildings – Exam Questions
Energy Transfers and Efficiency
a) Energy can be transferred usefully, stored, or dissipated, but
cannot be created or destroyed.
b) When energy is transferred only part of it may be usefully
transferred, the rest is ‘wasted’.
c) Wasted energy is eventually transferred to the surroundings,
which become warmer. The wasted energy becomes increasingly
spread out and so becomes less useful.
d) To calculate the efficiency of a device using:
Energy Transfers and Efficiency
The energy efficiency of a device can be calculated using this
formula:
energy efficiency =
useful output energy
total input energy
 Useful energy is measured in joules (J).
 Total energy is measured in joules (J).
 Energy efficiency does not have any units.
It is a number between 0 and 1 which can be converted
into a percentage by multiplying by 100.
Energy Transfers and Efficiency
All the energy transfers (useful
and wasted) that are
associated with a device can
be represented by a Sankey
diagram.
A Sankey diagram uses arrows
to represent all the output
energies.
The thickness of each arrow is
proportional to the amount of
energy involved at that stage.
Filament light bulb
100 J
10J
electrical
light
energy
energy
(input)
(output)
90J
heat energy
(wasted)
Energy efficient light bulb
20J
10J
electrical
light
energy
energy
(input)
10J (output)
heat energy
(wasted)
Energy Transfers and Efficiency – Exam Questions
Transferring Electrical Energy
a) Examples of energy transfers that everyday electrical appliances
are designed to bring about.
b) The amount of energy an appliance transfers depends on how
long the appliance is switched on and its power.
c) To calculate the amount of energy transferred from the mains
using:
Energy transferred = power x time
d) To calculate the cost of mains electricity given the cost per
kilowatt-hour.
Transferring Electrical Energy
The amount of electrical energy (i.e. the amount of electricity) used
by an appliance depends on its power and how long
the electricity is used for.
electrical energy = power x time
Power is measured in kilowatts (kW) and the time is measured in
hours (h), so what are the units of electricity measured in?
1 unit of electricity = 1 unit of electrical energy
= 1 kilowatt hour (kWh)
Example:
How many units of electricity is 17.6 kWh?
17.6 units
Transferring Electrical Energy
Electricity costs money, which is why
every home has an electricity meter.
The meter records how much
electricity is used in a house in
units of electrical energy.
The units of electrical energy are
called kilowatt hours (kWh).
The cost of an electricity bill is calculated from the number of
units used.
Transferring Electrical Energy
The cost of electricity is the number of units of electrical
energy multiplied by the cost per unit.
cost = number of units x cost per unit
Example:
How much would 10 units of electricity cost at a price of 9p
per unit?
cost = 10units x 9p/unit
= 90p
Transferring Electrical Energy
A kettle uses 45.2 kWh of energy.
If electricity costs 10 p per unit, how
much does it cost to use the kettle?
Number of units:
number of units of electricity = number of kilowatt hours
= 45.2 units
Cost of electricity:
cost = number of units x cost per unit
= 45.2 units x 10 p / unit
= 452 p or £4.52
Transferring Electrical Energy – Exam Questions
Transferring Electrical Energy – Exam Questions
Generating Electricity
a) In some power stations an energy source is used to heat water. The steam
produced drives a turbine that is coupled to an electrical generator.
Energy sources include:
the fossil fuels (coal, oil and gas) which are burned to heat water or air
uranium and plutonium, when energy from nuclear fission is used to
heat water
biofuels that can be burned to heat water.
b) Water and wind can be used to drive turbines directly.
c) Electricity can be produced directly from the Sun’s radiation.
d) In some volcanic areas hot water and steam rise to the surface. The steam can
be tapped and used to drive turbines. This is known as geothermal energy.
e) Small-scale production of electricity may be useful in some areas and for some
uses, e.g. hydroelectricity in remote areas and solar cells for roadside signs.
f) Using different energy resources has different effects on the environment.
These effects include:
the release of substances into the atmosphere, the production of waste
materials, noise and visual pollution, the destruction of wildlife habitats.
Generating Electricity
Energy resources can be classified into two groups.
Non-renewable
Renewable
Renewable energy resources can
be replaced or regenerated and
will never run out (at least not for
a very long time).
Non-renewable energy
resources will eventually
run out – once used they
cannot be used again.
Examples: wind and solar.
Examples: coal and oil.
Generating Electricity
Generating Electricity
Generating Electricity – Exam Questions
Generating Electricity – Exam Questions
The National Grid
a) Electricity is distributed from power stations to consumers along
the National Grid.
b) For a given power increasing the voltage reduces the current
required and this reduces the energy losses in the cables.
c) The uses of step-up and step-down transformers in the National
Grid.
The National Grid
Power station
Step up
transformer
Step down
transformer
Homes
 The voltage is altered in The National Grid with the use of step-up
and step-down transformers.
 The voltage is ‘stepped up’ when it leaves the power station to
reduce the current - this reduces the amount of energy loss
 The voltage is then ‘stepped down’ before it reaches our homes
The National Grid – Exam Questions
Waves
a) Waves transfer energy.
b) Waves may be either transverse or longitudinal.
c) Electromagnetic waves are transverse, sound waves are longitudinal
and mechanical waves may be either transverse or longitudinal.
d) All types of electromagnetic waves travel at the same speed through
a vacuum (space).
e) Electromagnetic waves form a continuous spectrum.
f) Longitudinal waves show areas of compression and rarefaction.
g) Waves can be reflected, refracted and diffracted.
h) Waves undergo a change of direction when they are refracted at an
interface.
i) The terms frequency, wavelength and amplitude.
j) All waves obey the wave equation: v = f x 
k) Radio waves, microwaves, infrared and visible light can be used for
communication.
Transverse Waves
Vibrations
Vibrations
Wave Direction
The vibrations are at 90O or right angles to the
direction of the waves.
Transverse Waves
Certain parts of a transverse wave have special names.
The high points of a transverse wave are called peaks and the
low points of a transverse wave are called troughs.
peak
trough
Transverse Waves
The wavelength of any wave is the distance between two
matching points on neighbouring waves.
wavelength
wavelength
wavelength
The wavelength is the same whichever two matching points are
used to measure this distance.
The symbol used to represent wavelength is .
Transverse Waves
The amplitude of any wave is the maximum distance a point
moves from its rest position.
amplitude
amplitude
The amplitude of a transverse wave is the height of a peak or trough
from the wave’s rest position of the wave.
The larger the amplitude, the greater the energy of the wave.
Transverse Waves
The frequency is the number of waves passing any point each
second.
 frequency = number of waves past a point / time
 frequency is measured in hertz (Hz)
 1 wave per second = 1 Hz
If this set of transverse waves pass a point in one second, what
is the frequency?
4 Hz
Longitudinal Waves
Vibrations
Wave Direction
The vibrations are parallel to the direction of the waves.
Longitudinal Waves
Where the particles in a longitudinal wave bunch together are
called compressions, where they spread out are called
rarefactions.
Longitudinal Waves
The wavelength of a longitudinal wave is measured from one
compression to another, or one rarefaction to another.
wavelength
wavelength
Waves
For any set of waves, the wave speed (v) can be calculated from the
frequency (f) and wavelength () using this formula:
wave speed = frequency x wavelength
v = fx
What are the units of speed, frequency and wavelength?
 Wave speed is measured in metres per second (m/s).
 Frequency is measured in hertz (Hz).
 Wavelength is measured in metres (m).
Waves
These waves are travelling across the
surface of a pond. The length of each
wave is 0.25 m.
Two waves pass the duck each second,
so the frequency is 2 Hz.
This means that the waves travel 0.5 m
each second, so the speed of the waves
is 0.5 m/s.
From this example, the connection between speed, frequency and
wavelength is:
speed = frequency x wavelength
0.5 m/s =
2 Hz
x
0.25 m
Waves – Exam Questions
Waves – Exam Questions
Reflection
a) The normal is a construction line perpendicular to the
reflecting surface at the point of incidence
b) The angle of incidence is equal to the angle of reflection.
c) The image produced in a plane mirror is virtual, upright and
laterally inverted.
Reflection
A plane mirror reflects light
regularly so it produces a clear
image, which is the same size
as the object.
The image appears the same
distance behind the mirror as
the object is in front of it.
What is different about the
image compared to the object?
When an object is reflected in a plane mirror, left appears as right
and right appears as left. This type of reversal is called lateral
inversion.
Reflection – Exam Questions
Sound
a) Sound waves are longitudinal waves and cause vibrations in a
medium, which are detected as sound.
b) The pitch of a sound is determined by its frequency and
loudness by its amplitude.
c) Echoes are reflections of sounds.
Sound
Sound waves can be studied with this type of equipment.
loudspeaker
oscilloscope
signal generator
A loudspeaker
converts signals
from the signal
generator into
sound waves.
A signal generator
produces different
types of signals.
An oscilloscope
shows wave patterns
and allows us to ‘see’
sound.
Sound
A sound can be quiet or loud.
quiet sound
loud sound
On an oscilloscope trace, the loudness of a sound is shown by the height of
the wave. This is called the amplitude.
Which word should be crossed out in this sentence?
The larger the amplitude of the wave on the trace, the
louder/quieter the sound.
Sound
Which trace represents the loudest sound?
A
Sound A is the loudest.
B
Sound A has the largest amplitude (i.e. the tallest waves), so it is
the loudest of these two sounds.
Sound
A sound can be high or low – this is the pitch of the sound.
low pitch sound
high pitch sound
On an oscilloscope trace, the pitch of a sound is shown by how many waves
there are. This is called the frequency.
Which word should be crossed out in this sentence?
The greater the number of waves across the oscilloscope trace, the
lower/higher the frequency and pitch.
Sound
Which trace represents the sound with the highest pitch?
A
B
Sound B has the highest pitch.
Sound B has the most number of waves across the
oscilloscope – it has the highest frequency and so has the
highest pitch.
Sound
What happens when a sound wave meets a hard flat surface?
The sound wave is reflected back from the surface.
This is called an echo.
Sound – Exam Questions
Red Shift and the Big Bang Theory
a) If a wave source is moving relative to an observer there will be a
change in the observed wavelength and frequency. This is known as the
Doppler effect.
b) There is an observed increase in the wavelength of light from most
distant galaxies. The further away the galaxies are, the faster they are
moving, and the bigger the observed increase in wavelength. This effect
is called red-shift.
c) How the observed red-shift provides evidence that the universe is
expanding and supports the ‘Big Bang’ theory (that the universe began
from a very small initial point).
d) Cosmic microwave background radiation (CMBR) is a form of
electromagnetic radiation filling the universe. It comes from radiation
that was present shortly after the beginning of the universe.
e) The ‘Big Bang’ theory is currently the only theory that can explain the
existence of CMBR.
Red Shift and the Big Bang Theory
The Doppler effect means that sound
moving away from an observer appears to
be lower in frequency.
The same thing happens with light from
distant galaxies, which appears to be
shifted towards the low frequency, red end
of the spectrum.
This means the distant galaxies must be
moving away from the Earth.
It has also been observed that the further away a galaxy is, the
greater the amount of red shift.
This means that very distant galaxies must be moving faster
than near, all of which is evidence for the Big Bang theory.
Red Shift and the Big Bang Theory
The observation of red shift is a key piece of evidence for the Big
Bang theory about the origin of the Universe.
This states that the Universe ‘began’ with a colossal explosion
13,700 million years ago and has been expanding ever since.
The other key piece of evidence for the
Big Bang theory is cosmic microwave
background radiation (CMBR).
CMBR is radiation remaining
from the Big Bang explosion
and fills the whole of the Universe.
Red Shift and the Big Bang Theory
• The Big Bang is the most
widely recognised scientific
theory on how the Universe
began.
• It states that the Universe
began from a very small,
very dense and very hot
initial point.
• It burst outwards in a
great explosion, and all
matter and space was
created in the Big Bang.
• It is even thought that
this was the moment when
time began.
Red Shift and the Big Bang Theory
• The first piece of evidence for the
Big Bang is from data collected on
red-shift.
• Red-shift shows us that galaxies
which are furthest away from us are
moving faster than galaxies closer
to us.
• The galaxies are a bit like coloured
sparks from an exploding firework.
The sparks moving fastest travel the
furthest.
• If you could run time backward
you would see the sparks all starting
in one point. The same is true for
galaxies.
Red Shift and the Big Bang Theory
• In the 1960s two scientists called Wilson and Penzias noticed that a form of
microwave radiation was affecting their readings.
• The electromagnetic radiation was everywhere and is now called cosmic microwave
background radiation (CMBR).
• CMBR is explained as being heat left over from the Big Bang.
• As the Universe exploded, it cooled and the radiation was stretched out. Today this
radiation is in the microwave region of the electromagnetic spectrum
Red Shift and the BBT – Exam Questions
Red Shift and the BBT – Exam Questions