Topic 1 Visible light and the Solar System

Topic 1 Visible light and the Solar System: 1. The Solar System 2. Refracting Telescope 3. Reflecting Telescope 4. Lenses 5. Waves

The Solar System Geocentric (Earth Centred) Ptolemy Heliocentric (Sun Centred) Copernicus BUT Galileo discovered 4 of Jupiter’s moons, he disproved Ptolemy completely as not everything orbited Earth! And the ORBITS are not perfectly spherical, they are elliptical

Refraction Light travels in straight lines. When it enters another material it bends at an interface (boundary). A line at 90 o to the interface is called the normal. Changes speed and direction.

Refraction in Lenses Converging lenses (Convex) focus parallel light to a focal point (convergence). The distance between these is the focal length. The fatter the lens the shorter the focal length. Focus light rays to a point, form image on paper, measure the focal length with a ruler.

Refraction in Telescopes The objective lens collects the light and forms an image The eyepiece lens magnifies the image

Real and Virtual Images A real image is the image formed where the light rays are focussed. A virtual image is one from which the light rays appear to come but don’t actually come from that image like in a mirror.

Problems with Refractive Telescopes • Due to light being reflected at boundaries the image that is processed will be fainter • If the star is already feint it will make it harder to detect • Refracting telescopes need to be very long to have a large magnification • Large lenses help magnification but they are heavy and difficult to mould into a perfect shape, this means that the images have distorted colours

Reflective Telescope

Waves Transfer Energy TRANSVERSE: Move at right angles to the vibration (Up and Down) LONGITUDINAL: Move in the same direction as the vibration (Left and Right)

Waves FREQUENCY: The number of waves that pass a point in a second WAVELENGTH

Topic 2: The Electromagnetic Spectrum 1. 2. 3. 4. 5. Beyond the Visible The EM Spectrum EM Dangers Using EM Radiation Ionising Radiation

Wave Equations WAVE SPEED = FREQUENCY X WAVELENGTH (m/s) (Hz) (m) WAVE SPEED = DISTANCE / TIME (m/s) (m) (s)

Herschel Ritter Split light with a prism, measured the heat with thermometers. As colours went from violet to red the temperatures increased. When he placed thermometer just beyond red it rose again. He has discovered infrared. Tried to find invisible light beyond the violet. He shone the light onto silver chloride. He found that the silver chloride turned black quicker towards the violet end of the spectrum. It turned black quickest just beyond violet. He discovered ultraviolet.

All Electromagnetic Waves are Transverse Can travel without any particles to vibrate In a vacuum they all travel at the speed of light 300, 000 km/s Visible light is made out of all the colours (ROYGBIV)

Dangers of EM Radiation All EM Waves carry energy. At a high frequency this energy is dangerous. Radiowaves- No danger Microwaves- Can internally boil blood Infrared- Surface burns Visible- Can cause temporary blindness UV- Can cause skin cancer X-Rays- Excessive exposure can cause cancer Gamma- Mutates DNA, cancer

Uses of EM Radiation Radio Waves- Communications, satellite, wifi Microwaves- Microwave ovens, mobile phones Infrared- cooking, optical fibres, thermal imaging Visible- human eyes, photography UV- Security markings, disinfectant of water X-Rays- Medical x-rays and airport scanners Gamma- sterilise food and medical equip, detect cancer, treat cancer in radiotherapy

Ionising Radiation Type of radiation Symbol What is it made from? How far will it travel? What stops it? Alpha Helium nucleus. 2 protons & 2 neutrons cm Air /paper Beta High speed electron m Aluminium High energy wave Lots of m Thick lead & concrete Gamma γ Alpha and Beta are not EM waves but they are ionising particles. Like Gamma they can be extremely dangerous as they can mutate DNA in cells

Topic 3: Waves and the Universe 1. 2. 3. 4. 5. 6. 7. The Universe Spectrometers Exploring the Universe Alien Life? Life-cycle of stars Theories of the Universe Red-shift

The Universe is made out of Everything! Galaxies, planets, stars, nebulae, black holes etc. Astronomers initially made observations with the naked eye. Galileo discovered that the Milky Way and some nebulae. Relative sizes of the universe are hard to imagine you can fit 30 Earths between the Earth and the Moon. The Sun is over 11, 000 ‘Earths’ away.

Spectroscopy The light is split into the visible spectrum. Black lines show up in the spectrum and signify what elements the star was made from. This kind of spectrum actually tells us the types of element present in the outer layers of the sun (they absorb some of the light given out by the core leaving the black lines. )

Exploring the Universe You can use telescopes to detect different wavelengths of the EM spectrum. However we have the problem that some of the spectrum is absorbed by the atmosphere (for safety). Because of this we need to place the telescopes in space so that the wavelengths are not absorbed. DO NOT SAY THAT THE CLOUDS ARE IN THE WAY OR TO BE ‘CLOSER TO THE OBJECT’

Earth is the only place where we know life exists Water is ESSENTIAL to life. Landers; land on the planet and explore the surface Probes; orbit the planet and photograph the surface Rovers; take close up photographs of the surface We have found other planets orbiting stars but they are too far away to produce a clear image. Search for Extra-terrestrial Intelligence (SETI): Analyse radio waves that have arrived at Earth from Space for a alien message (None have been found so far).

Life Cycle of a Star

Life Cycle of A Main Sequence Star 1. Life starts in a Nebula (a hot dense of dust & gas) As the cloud gets more dense it starts to collapse under gravity. As the mass gets larger, the gravitational pull does also. This creates a protostar. 2. Eventually the temperatures rise so much that the hydrogen atoms fuse together (fusion) to form helium and release a lot of energy. This star then becomes a main sequence star. 3. This will remain stable for billions of years until the star stops changing hydrogen into helium, the energy source stops and the star begins to collapse in on itself. The outer layers expand causing a red giant. 4. It will remain like this for another billion years before it releases its shell of gas. 5. The rest of the star is forced together under gravity to form a white dwarf. 6. Theoretically it is said that a white dwarf will eventually turn into a black dwarf but no evidence of this has been shown.

Life Cycle of a Higher Mass Star 1. Stars with more mass than the Sun tend to be hotter and burn faster 2. They fuse Hydrogen into Helium faster to become Super Red Giants. 3. They will then supernova, where the outer layers rapidly collapse and then explode. 4. If the star is not that massive the remains will be a neutron star. 5. If the star is 4 x more massive than the sun it will turn into a black hole through gravity. The gravitational pull is so strong that not even light can escape!

Red Shift Towards You Away From You BLUE SHIFT: the wavelength is shorter, moving towards you. RED SHIFT: the wavelength is longer. Moving away from you, if it is more red shift it is moving away faster and is more likely to be further away!

Theories of the Universe Big Bang Theory Steady State Theory All of the Universe and matter started out at a singular point of concentrated energy 13. 5 billion years ago. The universe is constantly expanding The Universe has always been there but is expanding New matter is constantly created as it expands Cosmic Microwave Background Radiation(CMB) Red shift Redshift

Topic 4: Waves and the Earth 1. Infrasound 2. 3. 4. 5. Ultrasound Seismic Waves Earthquakes Seismometers

Infrasound Any sound below 20 Hz is known as Infra-Sound. The human ear is not sensitive enough to detect either of these two types of wave however many other creatures are. Infrasound is very useful as it travels very long distances and can be used as a method of communication between animals and a way of detecting Earthquakes and Volcanoes.

Ultrasound is frequencies above 20, 000 Hz( 20 k. Hz). Some animals such as Dolphins use ultrasound for communication. Common uses of Ultrasound: Baby scans and SONAR devices. The ship emits a pulse of ultrasound This spreads out through the water and some of it hits the sea bed. A detector on the ship receives the echo and the SONAR equipment detects the time of the two. We then calculate it using s=d/t Remember that if you are calculating depth or distance you need to divide it by 2!

Ultrasound in Scans • A common use of ultrasound is to make images of babies so that doctors can detect how well the baby is developing • When the scan is made some of the waves are reflected every time they enter a new medium (material).

How do plates move? 1. 2. 3. 4. Convection currents in the magma (hot rises, cool falls). Friction between plates on the magma Build up of energy Energy is released (when they separate) in the form of a seismic wave.

P and S waves P or primary waves • fastest waves • travel through solids, liquids, or gases • compressional wave, material movement is in the same direction as wave movement UP and DOWN. LONITUDINAL S or secondary waves • slower than P waves • travel through solids only • shear waves - move material perpendicular to wave movement LEFT to RIGHT TRANSVERSE

How is an Earthquake’s Epicenter Located? By using seismic wave behavior – P waves arrive first, then S waves – Average speeds for all these waves is known – After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter. – You will usually triangulate (use three stations) between other stations, that are different distances away, to calculate the approximate epicenter.

Seismic waves tell you about the structure of the Earth as they refract at boundaries with different densities.

Topic 5: Generation and Transmission of Electricity 1. 2. 3. 4. 5. 6. Renewable Resources Non-Renewable Resources Generating Electricity Transmitting Electricity Paying for Electricity Reducing Energy Use

Renewable Resources Resource How they work: Advantages Disadvantages Solar cells heat air under glass, hot air rises and turns gen Have to be in a specific area, only works with light Tidal Tides move through a Direct energy transfer Have to have a tide dam turning a turbine Predictable Not available all year round Hydroelectric Falling water in high reservoirs Available at any time Started and stopped easily Wind Turns a wind turbine directly generating electricity Direct energy transfer Need a lot to produce electricity Dependant on wind Geothermal Heat is transferred by No harmful gasses hot underground No fuel cost rocks Wave Floating electrical Direct energy transfer Not predictable generators. Air forced Don’t work in bad up pipes, turns a gen weather Direct transfer of energy (non-lost) Reservoirs can dry up Need rainfall to refill them Need to be by a tectonic plate (location)

Non-Renewable Resources Resource Advantages Coal Formed from fossilised plants Ready-made fuel. When burned they It is relatively cheap give off to mine and to atmospheric convert into energy. pollutants, including greenhouse gases Oil A carbon-based liquid formed from fossilised animals. Gas Disadvantages

Generating Electricity Electromagnetic induction – creates a current in a wire when a wire is moved into a magnetic field The current can be increased by: • Using a coil of wire, or putting more turns on the coil • Using an iron core inside the coil of wire • Using stronger magnets • Moving the wire faster The direction of the current can be changed by changing the direction: • Of the movement of the wire • Of the magnetic field Direct current (DC) - current flows in one direction Alternating current (AC) – current changes direction Generators supply current with alternates in direction (AC)

Transmitting Electricity A transformer can change the size of an alternating current If the voltage passed through the nation grid is increased less energy is wasted as heat and the efficiency is improved Power stations convert 25 k. V to 400 k. V before the electricity is sent around the country • A step up transformer – increases the voltage and decreases the current. This happens between power station and transmission lines to stop heat being wasted. • A step down transformer – decreases the voltage and increases the current. This happens between local substations and homes to reduce the voltage for homes

POWER The amount of energy transferred in a second. P Power I V E T = X = Current x Voltage Watts(W) Amps (A) Volts (V) P Power Watts(W) = ÷ = Energy ÷ Time Joules (J) Seconds (s)

Cost of Electricity 1000 W = 1 k. W Remember that with this formula you need to identify: TIME is in HOURS COST is in PENCE (Unless stated otherwise) POWER is in KILOWATTS Cost of 1 hour is in PENCE

Reducing Energy Use Payback time= Cost / savings per year Years Pounds (£) Cost Efficient means which is the best value for money Payback time how long it will take to make the money back in relation to savings

Topic 6: Energy Transfers 1. Energy Transfer Diagrams 2. Sankey Diagrams 3. Efficiency 4. Heat Radiation 5. The Earth’s Temperature

Energy Transfers: how the energy is transferred to other forms. Types of Energy: 1. Chemical 2. Elastic Potential 3. Electrical 4. Gravitational Potential 5. Kinetic 6. Light 7. Nuclear 8. Sound 9. Thermal LAW OF CONSERVATION OF ENERGY: ENERGY IS NEVER CREATED OR DESTROYED, ONLY TRANSFERRED TO OTHER FORMS OR THE SURROUNDINGS

Energy Transfer Chain for a Torch

Conservation of Energy In physics we use the word system. This is something in which we are studying for changes. They can be very complex (eg, a planet), or quite simple (eg, a piece of metal) If you add up all the energy that has been transferred (Output) and compare it to the energy put in (Input), they should be the same. OUTPUT ENERGY = INPUT ENERGY

Sankey Diagrams: These show energy conservation, the width of the arrows represents the amount of energy in joules.

Efficiency How good a device is at converting energy into useful forms is know as its efficiency. Low energy light bulbs transfer more of the input electrical energy, into light electricity than older light bulbs which produce excess heat.

Efficiency Calculation

Heat Radiation Infrared radiation in the spectrum is heat. ALL objects are continually absorbing and radiating radiation. If an object is hotter than its surroundings it is radiating more heat than it absorbs! COLOURS & TEXTURE: Dark Matte surfaces absorb heat. They also emit more radiation than bright glossy surfaces. Silver reflect nearly all of the heat.

The Earth’s Temperature The Earth theoretically will try to radiate the same amount of energy it is absorbing. HOWEVER Greenhouse gasses trap some of the energy in the atmosphere so not all of it is re-radiated. This leads to (over a long period of time) an increase in the global temperature (global warming).

So what happens next…? There is only a certain amount of heat that additional green house gasses can absorb. 1. So if the greenhouse gas emissions are stopped that means that the temperature increase will also stop 2. If greenhouse gasses are removed, the temperature will decrease. 3. Scientists have came up with the idea of putting huge white screens into space to reflect the sunlight and shade the Earth. Another way is to place thousands of ping pong balls on the sea surface to do the same thing!

TIPS! 1. Answer the question that you can do first! Don’t always start with question one if you can’t do it! 2. Remember ENAU (Equation, Number, Answer Unit). You get marks for your working out! 3. Read the question!!! Go through your paper with a highligher or circle or underline key points! 4. Use every available minute 5. Make sure your accurate! 6. Remember SO WHAT? So what do I mean by that? 7. Write clearly, they need to be able to read what you have written to mark it! Good Luck!