23122021 Reflection nebula 23122021 Planetary nebula This nebula

23/12/2021 Reflection nebula

23/12/2021 Planetary nebula (This nebula is smaller and will only form a planet)

Stage 2: Protostar Gravity will slowly pull these particles together… As they move inwards their gravitational potential energy is converted into heat and a PROTOSTAR is formed 23/12/2021

Stage 3: Main Sequence 23/12/2021 In a main sequence star the forces of attraction pulling the particles inwards are _____ by radiation pressure acting outwards due to the huge _____ inside the star. Stars are basically ____ reactors that use _______ as a fuel. During its main sequence a star will release energy by converting hydrogen and helium (light elements) into _____ elements. Our sun is an example of a main sequence star – it’s in the middle of a 10 billion year life span Words – heavier, balanced, hydrogen, nuclear, temperatures

Stage 4: Red Giant 23/12/2021 Eventually the hydrogen and helium will run out. When this happens the star will become colder and redder and start to swell… If the star is relatively small (like our sun) the star will become a RED GIANT If the star is big (at least 4 times the size of our sun) it will become a RED SUPERGIANT

Stage 5: The Death 23/12/2021 What happens at this point depends on the size of the star… 1) For SMALL stars the red giant will collapse under its own gravity and form a very dense white dwarf: Red giant White dwarf Black dwarf

2) If the star was a RED SUPERGIANT it will shrink and then EXPLODE, releasing massive amounts of energy, dust and gas. 23/12/2021 This explosion is called a SUPERNOVA Before After

23/12/2021 The dust and gas on the outside of the supernova are thrown away by the explosion and the remaining core turns into a NEUTRON STAR. If the star is big enough it could become a BLACK HOLE.

Stage 6: Second generation stars 23/12/2021 The dust and gas thrown out by a supernova can be used to form a new star… Our sun is believed to be a “______ star” – this is because it contains some _____ elements along with hydrogen and ____. These heavier elements would have been the products of a previous star that have been thrown out by a ____. These heavier elements are also found on planets, indicating that they might have been made from remains of previous _______ as well. Words – helium, heavier, second generation, stars, supernova

The formation of the universe 23/12/2021 There are two main theories about how the universe started: The “Steady State” theory This theory states that the universe has always existed as it does now and hasn’t changed. The trouble is that the night sky would be completely lit up because of the billions of stars, but it’s not, so… The “Big Bang” theory This theory states that the universe started off with an explosion and everything has been moving away ever since. There are two main pieces of evidence for this: background microwave radiation and red shift.

23/12/2021 Evidence about the origins of the universe…

Microwaves 23/12/2021 When the “Big Bang” happened microwaves were produced and these are still reaching us now. They can sometimes be seen as TV interference.

Red Shift explained Source of light “Spectra” 23/12/2021

23/12/2021 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… Before helium After 23/12/2021

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 23/12/2021

Red Shift simplified 23/12/2021 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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23/12/2021 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 23/12/2021 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 14 _____ 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

Big Bang Theory vs Steady State 23/12/2021 Some scientists have explained that red shift can actually be used to support the Big Bang Theory – this explanation is based around the rates of expansion and contraction of different galaxies. If our neighbouring galaxy is expanding at a different rate to the Milky Way then it will appear red or blue-shifted. However, the discovery of CMBR was the final nail in the coffin for the Steady State theory. So, Mr President, the Big Bang theory is now the widely accepted theory of how the universe began. Stephen Hawking, 1942 -

23/12/2021 Topic 4 – Waves and the Earth

Ultrasound 23/12/2021 Ultrasound is the region of sound above 20, 000 Hz – it can’t be heard by humans. There a number of uses for ultrasound: 1) Pre-natal scanning 1) Sonar 2) Communication between animals

Pulse-Echo techniques 23/12/2021 In pulse-echo techniques sound is reflected from an object to measure the distance to that object:

Pulse-Echo techniques - Ultrasound 23/12/2021 Ultrasound is the region of sound above 20, 000 Hz – it can’t be heard by humans. It can be used in pre-natal scanning, sonar techniques and as communication between _______: How does it work? Ultrasonic waves are partly _____ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a _____ of the object. Words – depth, reflected, picture, medium, animals

The Maths of Pulse-Echo Consider shouting at a wall: x The speed of sound is given by: Therefore v = 2 x/t x = vt/2 23/12/2021

The Maths of Pulse-Echo 23/12/2021 The echo takes 0. 8 seconds to return and the speed of sound in water is 1500 ms-1. How deep is the water? 25 50 75 100 125 150 175 200 t/μs Use the ultrasound scan to determine the width of the amniotic sac and the width of the baby’s body. The speed of sound in the fluid is 1500 ms-1 and in soft tissue the speed is 1560 ms-1.

Using an oscilloscope with ultrasound 23/12/2021 Consider a block of metal with a flaw: 20 ms/div Q. If the speed of the ultrasonic wave is 3, 000 m/s how far away is the flaw from the detector?

Infrasound 23/12/2021 Infrasound is the region of sound BELOW 20 Hz (as opposed to ULTRASOUND which is above 20 KHz) – it can’t be heard by humans. Some uses: 1) Communication between animals African elephants use infrasound to communicate with other elephants many kilometres away. 2) Detecting movement in remote areas 3) Detecting volcanic eruptions and meteors

The Structure of the Earth 23/12/2021 A thin crust 10 -100 km thick A mantle – has the properties of a solid but it can also flow A core – made of molten nickel and iron. Outer part is liquid and inner part is solid How do we know this? These facts have all been discovered by examining seismic waves (earthquakes)

Seismic waves Earthquakes travel as waves through the Earth – we call them SEISMIC WAVES. There are two types: P waves: 1) They are longitudinal so they cause the ground to move up and down 2) They can pass through solids and liquids 3) They go faster through more dense material S waves: 1) They are transverse so they cause the ground to move from right to left 2) They ONLY pass through solids 3) They are slower than P waves 4) They go faster through more dense material 23/12/2021

Seismic waves 23/12/2021 These P waves are being reflected at the crust These P waves travel through the Earth and are refracted when they pass through a medium The paths of these waves are all curved because density is gradually changing These S waves cannot travel through the outer core as they only go through solids

Locating Earthquakes 23/12/2021 By measuring the time it takes the wave to travel to these locations the location of the earthquake can be found.

Movement of the Crust 23/12/2021 The Earth’s _______ is split up into different sections called ____ plates: These plates are moving apart from each other a few centimetres every _______ due to the ____ currents in the mantle caused by the ____ decay of rocks inside the core. Words – radioactive, crust, convection, tectonic, year

Plate Movements Earthquakes and volcanic eruptions can be common here Igneous Rock Oceanic Crust Mantle Convection Currents 23/12/2021 Magma

Topic 5 – Generation and Transmission of Electricity 23/12/2021

Electric Current Electric current is a flow of charge around a circuit + - e- Note that electrons go from negative to positive and are “pushed” by the voltage By definition, current is “the rate of flow of charge” e- 23/12/2021

Basic ideas… 23/12/2021 Electric current is when electrons start to flow around a circuit. We use an _____ to measure it and it is measured in ____. Potential difference (also called _______) is how big the push on the electrons is. We use a ____ to measure it and it is measured in ______, a unit named after Volta. Resistance is anything that resists an electric current. It is measured in _____. Words: volts, amps, ohms, voltage, ammeter, voltmeter

More basic ideas… If a battery is added the current will ____ because there is a greater _____ on the electrons If a bulb is added the current will _______ because there is greater ____ in the circuit 23/12/2021

Electrical Power 23/12/2021 Power is defined as “the rate of transferring energy” and is measured in units called “Watts” (W). The amount of power being transferred in an electrical device is given by: Power = voltage x current in W in V in A P V I 1) How much power is transferred by a 230 V fire that runs on a current of 10 A? 2) An electric motor has a power rating of 24 W. If it runs on a 12 V battery what current does it draw? 3) An average light bulb in a home has a power rating of 60 W and works on 230 V. What current does it draw?

Fuels 23/12/2021 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… 23/12/2021 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

23/12/2021 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 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

Efficiency of Power Stations 23/12/2021 15 Heat J Heat 50 5 J J 100 J Boiler 85 J Heat Turbine Heat 35 J Kinetic Generator 30 J Electrical

Pollution 23/12/2021 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 23/12/2021 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 Different power stations have different start up times: Gas Quick Oil Coal Nuclear Slow 23/12/2021

Non-renewable energy sources Advantages Disadvantages Pollution – CO 2 leads to global warming and SO 2 leads to acid rain Cheap fuel costs Generate a lot of energy Easy to use 23/12/2021 Coal, oil, gas and nuclear Fuel will run out