12/03/2014
Physics Unit 1
(AQA)
Particle theory revision
12/03/2014
Particle theory is all about explaining the properties of solids,
liquids and gases by looking at what the particles do.
View animation
SOLIDS
In a solid the particles ______
around a _____ position. There
is a ______ force of attraction
between each particle and they
are very _____ together
Words – strong, close, vibrate, fixed
LIQUIDS
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In a liquid the particles are
_____ together but can move in
any direction. They won’t keep a
_____ shape like _____ do.
GASES
In a gas the particles are very
far apart and move _____ in all
directions. They often ______
with each other and because
they are far apart they can be
easily _______.
Words – fixed, collide, quickly, close, squashed, solids
Heat and Temperature
12/03/2014
Heat is a type of energy that will flow from a warm area
to a colder one. For example…
This cup of coffee will ____ ____
because it is _____ ____ heat energy
into the surroundings. The hotter it
is, the quicker it will lose heat.
This drink (taken out of the
fridge) will _____ ___ because it
is _____ ___ heat energy from
the surroundings.
Words – giving out, warm up,
taking in, cool down
Conduction
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Conduction is all about when heat is transferred through a
_________. The heat is passed on by ___________ in the
molecules. These vibrations get BIGGER when the solid has
more ENERGY (i.e. when it is being __________).
Heating a non-metal
Heating a metal
Metals are _______ conductors than non-metals. This is
because the heat is carried by free ________ that can
carry the energy around the metal and give it to other
electrons and ions.
Words – vibrations, electrons, solid, heated, better
Convection
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Convection is all about when a gas or liquid
(“fluid”) moves and carries heat with it. When
the fluid is heated it ____________. This
means that it will become less __________
than the colder fluid around it. Because of
this the warmer fluid will try to “_______”
over the colder fluid, and this is why warm air
rises. This is called a convection
___________. This is how heat reaches us
from the ___________ in this room.
In CONDUCTION the heat was passed on
by VIBRATIONS in a SOLID
In CONVECTION the heat is passed on by
the FLUID expanding, rising and TAKING
THE HEAT with it
Words to use: expands, radiators, dense, heated, current, float
Some questions on convection…
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1) Freezers in supermarkets are often left open to the
air. Explain why the food does not melt easily.
2) Explain why a hot air balloon rises in the air.
3) Explain why an ice cube floating at the top of a drink
will cool all of the drink.
4) Explain why, in a hot water tank in a house, the hot
water pipe might be located at the top of the tank.
Radiation
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An introduction…
I’m cool!
I’m very hot!
Some examples of radiation
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Some examples of radiation
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Radiation Practical
Time / min
Temperature in each container / 0C
Black
1
2
3
4
5
6
7
8
9
10
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Silver
Clear
Radiation
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Radiation is when heat moves around in electromagnetic _________ like
light does. Any hot object will emit heat radiation – the hotter it is, the
more radiation it emits. This type of radiation is called __________, and
too much of it will cause _________. Dark, matt colours will absorb AND
emit the _____ infra-red radiation, and light, shiny colours will ________
it.
The main difference with radiation is that conduction and convection could
ONLY happen in solids, liquids or gases, whereas radiation will happen
through an _____ _____. This is just as well, as otherwise we wouldn’t be
able to get any heat from the ___.
Words – sun, reflect, infra-red, waves, most, empty space, sunburn
Anything HOT emits HEAT RADIATION – the hotter it
is, the more infra red radiation it emits
Understanding Heat Transfer
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1) Explain how and where all 3 processes
of heat transfer happen in a bonfire
2) By considering how a Thermos
Flask is built explain how it
manages to keep hot drinks hot
and cold drinks cold.
Understanding Heat Transfer 2
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3) Car radiators are
designed to help car
engines lose heat. Explain
how they do this.
4) Some houses have solar collectors on their roof. Explain
how they work:
Understanding Heat Transfer 3
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5) Using your knowledge of heat transfer
explain how radiators heat a room and how
they are designed to efficiently do this.
6) Devices like computers have “heat
sinks” that are designed to help the
computer cool down. How are they
designed to help do this job?
Evaporation
12/03/2014
As well as through conduction, convection and radiation heat
can also be lost through evaporation:
View animation
Evaporation is when particles of liquid have enough energy to
“escape” from the rest of the liquid. Every time a particle
“escapes” it takes some heat energy with it.
Questions on understanding evaporation:
1) Why are swimming pool changing rooms always warm?
2) What conditions would a wet object dry out the quickest
in?
3) What’s the difference between evaporation and boiling?
Rate of Heat Transfer
12/03/2014
The rate at which an object cools down depends on:
1) It’s shape – the bigger the surface area, the ______ the
heat loss
2) It’s mass – the _____ the object, the slower the heat loss
3) The type of material – objects that are better _________
will lose heat quicker
4) What the material is in contact with – the _______ the
conductor, the quicker the heat loss
5) The temperature difference – the ______ the
temperature difference, the quicker the heat loss
Words – heavier, conductors, bigger, quicker, better
Heat loss in animals
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How are these animals adapted or behaving in a way that
maximises or minimizes heat loss?
Heat Loss from a House
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House insulation
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Loft insulation
Cavity wall
insulation
Double
glazing
Draught excluders
House insulation
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Type of insulation
Cost
Annual amount
saved
Loft insulation
£400
£80
Double Glazing
£2,000
£50
Cavity wall ins.
£600
£60
Draught excluder
£40
£20
1) Which type of insulation costs the most?
2) Which type of insulation is the most effective?
3) Which type is the most “cost effective”?
4) Which type pays for itself after 40 years?
U Values
12/03/2014
“U Values” are an industrial measure of how much heat is lost
through different materials.
Calculating a U value:
U value =
Rate of energy loss
Surface area x temperature difference
Q. Would you want the U value for your
house to be high or low?
U Values
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The lower a U value, the better the material is at keeping heat
in.
Some examples of U values and the effect of insulation:
Structure
Insulation level
U value
Roof
Without insulation
2.3
With insulation
0.4
Without insulation
1.6
With insulation
0.6
Without insulation
0.9
With insulation
0.6
Cavity wall
Floor
How Humans cope with being cold
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Specific Heat Capacity
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This can be thought of as “the capacity of an object to store
heat”. Consider some water:
If we heat this beaker up it’s fairly
clear that the amount of energy it gains
depends on how much water there is and
how hot it gets…
Energy is proportional to mass x
temperature rise
Energy = mass x s.h.c x temp
E = mcΔθ
Some example questions
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1) A beaker filled with 100g of water with specific heat
capacity 4200J/(kg.0C) is heated from 200C to 800C.
Calculate the amount of heat energy gained by the water.
25.2 KJ
2) Another beaker containing 24g of water starts at 500C. If
it loses 2000J of energy what temperature has it dropped
to?
30.20C
Applying Specific Heat Capacity
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1) Night storage heaters often contain
blocks of concrete or other materials of
high specific heat capacity. Explain how
they work.
2) Radiators can either be filled with
water or filled with oil. What are the
advantages and disadvantages of each?
Reducing Energy Consumption
12/03/2014
60W older bulb, roughly
70p, to be banned in the
EU from 2012.
25W “energy
efficient” light
bulb, £7.30 on
Amazon
Which one is more cost-effective?
The 9 types of energy
Type
Heat
Kinetic (movement)
Nuclear
Sound
Light
Chemical
Electrical
Gravitational potential
Elastic potential
3 example sources
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The Laws of Physics
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There are many laws of physics, but one of the most important
ones is:
Energy cannot be created or
destroyed, it can only be converted
from one form to another
Energy changes
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To describe an energy change for a
light bulb we need to do 3 steps:
1) Write down the
starting energy:
2) Draw an arrow
Electricity
3) Write down
what energy types
are given out:
Light + heat
What are the energy changes for the following…?
1) An electric fire
2) A rock about to drop
3) An arrow about to be fired
Conservation of Energy
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In any energy change there is ALWAYS some “waste” energy:
e.g. a light bulb:
Electricity
Light
+
heat
In this example HEAT is wasted and it is transferred to
the surroundings, becoming very difficult to use.
Describe the following energy changes and state the “waste”
energy or energies:
1) A vacuum cleaner
2) A TV
3) A dynamo/generator
Efficiency
12/03/2014
Efficiency is a measure of how much USEFUL energy you
get out of an object from the energy you put INTO it.
For example, consider a TV:
Electrical
Energy (200J)
Sound (40J)
Efficiency = Useful energy out
Energy in
x100%
Some examples of efficiency…
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1) 5000J of electrical energy are put into a motor. The
motor converts this into 100J of movement energy. How
efficient is it?
2) A laptop can convert 400J of electrical energy into 240J
of light and sound. What is its efficiency? Where does
the rest of the energy go?
3) A steam engine is 50% efficient. If it delivers 20,000J of
movement energy how much chemical energy was put into
it?
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Energy Transfer (“Sankey”) diagrams
Consider a light bulb. Let’s say that the bulb runs on 100
watts (100 joules per second) and transfers 20 joules per
second into light and the rest into heat. Draw this as a
diagram:
“Input” energy
100 J/s
electrical
energy
“Output” energy
20 J/s
light energy
80 J/s heat
energy (given to
the surroundings)
Example questions
Consider a kettle:
2000 J/s
electrical
energy
Sound
energy
Wasted
heat
Heat to
water
1) Work out each energy value.
2) What is the kettle’s
efficiency?
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Consider a computer:
150 J/s
electrical
energy
10 J/s
wasted
sound
20 J/s
wasted
heat
Useful
light and
sound
1) How much energy is converted
into useful energy?
2) What is the computer’s
efficiency?
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What happens if electricity isn’t available?
Advantages and
disadvantages?
Energy and Power
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The POWER RATING of an appliance is simply how much
energy it uses every second.
In other words, 1 Watt = 1 Joule per second
E = Energy (in joules)
E
P = Power (in watts)
T = Time (in seconds)
P
T
Some example questions
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1) What is the power rating of a light bulb that transfers 120
joules of energy in 2 seconds?
2) What is the power of an electric fire that transfers
10,000J of energy in 5 seconds?
3) Rob runs up the stairs in 5 seconds. If he transfers
1,000,000J of energy in this time what is his power rating?
4) How much energy does a 150W light bulb transfer in a) one
second, b) one minute?
5) Jonny’s brain needs energy supplied to it at a rate of 40W.
How much energy does it need during a physics lesson?
6) Lloyd’s brain, being more intelligent, only needs energy at a
rate of about 20W. How much energy would his brain use
in a normal day?
The Cost of Electricity
12/03/2014
Electricity is measured in units called “kilowatt hours” (kWh).
For example…
A 3kW fire left on for 1 hour uses 3kWh of energy
A 1kW toaster left on for 2 hours uses 2kWh
A 0.5kW hoover left on for 4 hours uses __kWh
A 200W TV left on for 5 hours uses __kWh
A 2kW kettle left on for 15 minutes uses __kWh
The Cost of Electricity
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To work out how much a device costs we do the following:
Cost of electricity = Power (kW) x time (h) x cost per kWh (p)
For example, if electricity costs 8p per unit calculate the cost
of the following…
1) A 2kW fire left on for 3 hours
48p
2) A 0.2kW TV left on for 5 hours
8p
3) A 0.1kW light bulb left on for 10 hours
8p
4) A 0.5kW hoover left on for 1 hour
4p
Reading Electricity Meters
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1) How many units of electricity
have been used?
2) If 1 unit costs 10p how much
has this electricity cost?
Fuels
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A “fuel” is something that can be burned to release heat and
light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In
other words, they were made from fossils.
Some definitions…
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A renewable energy source is clearly one that can be
_______ (“renew = make again”), e.g. _____, solar power
etc.
A ___________ energy source is one that when it has
been used it is gone forever. The main examples are
____, oil and gas (which are called ______ ____, as they
are made from fossils), and nuclear fuel, which is nonrenewable but NOT a fossil fuel.
Words – non-renewable, coal, fossil
fuels, wood, renewed
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Using non-renewable fuels in power stations
1) A fossil fuel is burned in the boiler
2) Water turns to steam and the steam drives a
turbine (in some gas poer stations the air is
heated directly)
3) The turbine turns a generator
4) The output of the generator is connected to a
transformer
5) The steam is cooled down in a cooling tower and
reused
Pollution
12/03/2014
When a fuel is burned the two main waste products are _____
dioxide and ________ dioxide.
Carbon dioxide is a _________ ___ and helps cause _______
_________. This is produced when any fossil fuels are
burned.
Sulphur dioxide, when dissolved in ________, causes ______
_____. This is mainly a problem for ___ power stations.
Nuclear power stations do not produce these pollutants
because they don’t ____ fossil fuels.
Words – sulphur, coal, global warming, carbon,
acid rain, greenhouse gas, rainwater, burn
Nuclear power stations
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These work in a similar way to normal power stations:
The main difference is that the nuclear fuel is NOT
burnt – it is used to boil water in a “heat exchanger”
Start up times
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Different power stations have different start up times:
Gas
Quick
Oil
Coal
Nuclear
Slow
Non-renewable energy sources
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Advantages
Disadvantages
Cheap fuel costs
Costs a lot of
money to
decommission a
nuclear plant
Good for “basic
demand”
Reliable
Coal, oil, gas and
nuclear
Fuel will run
out
Short start-up time for
gas and oil
Nuclear produces little
pollution
Pollution – CO2 leads to
global warming and SO2
leads to acid rain
Using Renewable fuels to drive the
turbine - Biomass
12/03/2014
Biofuels
Biomass can be used as a fuel in a number of ways:
1) Fast-growing trees that can be ____
2) Manure or other waste that can be
used to release _______ (biogas)
3) Corn or sugar cane that can be broken
down in a fermenter to produce
______ like bio-ethanol.
Biofuels have two main advantages
over traditional fuels – they are
______ and ________. However,
they still release ______ _______.
Words – alcohols, cleaner, burnt,
renewable, methane, carbon dioxide
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Carbon capture
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The trouble with burning fuels is that it leads to the release of carbon
dioxide, a greenhouse gas.
To help stop this problem, the carbon can be “captured”. Good examples of
this are underground oil and gas fields:
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Other ways of generating electricity
Can we drive the turbine directly
without burning any fossil fuels or
biomass?
Wind Power
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Tidal Power
High
tide
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Low
tide
Wave Power
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Hydroelectric Power
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Matching supply and demand
with hydroelectricity
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Hydroelectric power
station might “kick in” here
“Baseline” power stations
Renewable energy sources summary
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Advantages
Disadvantages
Zero fuel costs
Unreliable
(except for
hydroelectric)
Don’t produce
pollution
Hydroelectric
is good for a
“sudden”
demand
Solar is good for
remote locations
(e.g. satellites)
Wind, tidal,
hydroelectric and solar
Expensive
to build
Tidal barrages destroy the
habitats of wading birds
and hydroelectric schemes
involve flooding farmland
Solar Panels and Thermal Towers
12/03/2014
What are the energy
changes in the solar
cells and in the thermal
tower?
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Using Solar Energy in remote places
Geothermal Energy
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Geothermal energy can be used in _______ areas such as
______. In a geothermal source cold water is pumped down
towards ____ _____. The water turns to steam and the
steam can be used to turn ______. In some areas the _____
rising at the surface can be captured and used directly.
Words – steam, Iceland, volcanic, turbines, hot rocks
Electricity Supply in the UK
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The National Grid
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Electricity reaches our homes from power stations through the National
Grid:
Power station
Step up
transformer
Step down
transformer
Homes
If electricity companies transmitted electricity at 240 volts through
overhead power lines there would be too much ______ loss by the time
electricity reaches our homes. This is because the current is ___. To
overcome this they use devices called transformers to “step up” the
voltage onto the power lines. They then “____ ____” the voltage at the
end of the power lines before it reaches our homes. This way the voltage
is _____ and the current and power loss are both ____.
Words – step down, high, power, low, high
Power Lines
Here’s my new shed. I
want to connect it to the
electricity I my house.
Should I use an overhead
cable or bury the cable
underground?
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An introduction to Waves
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Some definitions…
1) Amplitude – this is
“how high” the wave is:
2) Wavelength () – this is the
distance between two
corresponding points on the
wave and is measured in metres:
3) Frequency – this is how many waves pass by
every second and is measured in Hertz (Hz)
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“Wave behaviour”
Anything that travels as a
wave demonstrates wave
behaviour – in other words, it
can be reflected, refracted
and diffracted:
Reflection
Refraction
Diffraction
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Transverse vs. longitudinal waves
Transverse waves are
when the displacement
is at right angles to
the direction of the
wave (e.g. light and
other electromagnetic
waves)…
Displacement
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Displacement
Direction
Direction
Longitudinal waves
are when the
displacement is
parallel to the
direction of the wave
(e.g. sound waves)…
Where are the compressions and rarefactions?
The Electromagnetic Spectrum
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Each type of radiation shown in the electromagnetic spectrum has a
different wavelength and a different frequency:
High frequency,
_____ wavelength
Gamma
rays
X-rays
Low frequency, _____
(high) wavelength
Ultra violet
Visible
light
Infra red
Microwaves
Radio/TV
γ
Each of these types travels at the same speed through a _______
(300,000,000m/s), and different wavelengths are absorbed by different
surfaces (e.g. infra red is absorbed very well by ___________ surfaces).
This absorption may heat the material up (like infra red and _______) or
cause an alternating current (like in a __ _______).
Words – black, microwaves, long, short, TV aerial, vacuum
The Electromagnetic Spectrum
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Type of radiation
Uses
Dangers
Gamma rays
Treating cancer,
sterilisation
Cell mutation
X rays
Medical
Cell mutation
Ultra violet
Sun beds
Skin cancer
Visible light
Seeing things
None (unless you
look at the sun)
Infra red
Remote controls,
heat transfer
Sunburn
Microwaves
Satellites, phones
Very few
TV/radio
Communications
Very few
The Wave Equation
12/03/2014
All E-M waves obey the Wave Equation:
Wave speed (v) = frequency (f) x wavelength ()
in m/s
in Hz
in m
V
f

Some example wave equation questions
12/03/2014
1) A water wave has a frequency of 2Hz and a wavelength
of 0.3m. How fast is it moving?
0.6ms-1
2) A water wave travels through a pond with a speed of
1ms-1 and a frequency of 5Hz. What is the wavelength
of the waves?
0.2m
3) The speed of sound is 330ms-1 (in air). When Dave
hears this sound his ear vibrates 660 times a second.
What was the wavelength of the sound?
0.5m
4) Purple light has a wavelength of around 6x10-7m and a
frequency of 5x1014Hz. What is the speed of purple
light?
3x108ms-1
How sound travels…
12/03/2014
As we know, sound waves are formed when something vibrates.
But how does the sound reach our ears?
Air molecules
1) An object
makes a
sound by
vibrating
2) The vibrations pass
through air by making
air molecules vibrate
3) These
vibrations are
picked up by
the ear
Transmitting information
12/03/2014
Although E-M radiation travels in straight lines, we can send infra-red and
light signals around a curved path using an optical fibre:
Optical fibres have two main advantages: they can send more information
compared to electrical cables of the same diameter and with less signal
weakening.
Microwaves are used by satellites
because they can pass through the
Earth’s atmosphere:
Microwaves are also used in
mobile phone networks.
Reflection
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Angle of incidence = Angle of reflection
Normal
Reflected ray
Incident ray
Angle of
incidence
Angle of
reflection
Mirror
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Evidence about the origins of
the universe…
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Source of
light
“Spectra”
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If you pass the light through a gas something
different is seen…
helium
Some wavelengths of light
are absorbed by the gas –
an “absorption spectrum”.
If the light source is moving away the absorption
spectra look a little different…
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Before
helium
helium
After
The absorption lines have all been “shifted”
towards the longer wavelength end (red end)…
This is called red
shift. The faster
the light source
moves the further
its light will be
“shifted”
Before
After
A similar effect happens with sound –
this is called “The Doppler Effect”
Hear Doppler Effect
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Red Shift simplified
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Basically, if I walk towards you I’ll look
slightly more blue. Then, if I walk away
from you, I’ll look slightly more red!!
Let’s try it…
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Light from different stars and from the edge
of the universe also shows this “red-shift”.
This suggests that everything in the universe
is moving away from a single point.
This is the BIG
BANG theory
Red shift summary
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Light from other galaxies has a longer _________ than expected. This
shows that these galaxies are moving ____ from us very quickly. This
effect is seen to a greater extent in galaxies that are _______ away from
us. This indicates that the further away the galaxy is, the ______ it is
moving.
This evidence seems to suggest that
everything in the universe is moving
away from a single point, and that this
process started around 15 _____
years ago. This is the ____ ________
Theory. Further evidence of this
theory is Cosmic Microwave
Background Radiation (CMBR) – this
radiation comes from the Big Bang and
fills the _________.
Words to use – faster, away, universe, big
bang, billion, wavelength, further