P1-3 Long Answer Ideas Use the collection of points for each question to help check that you have covered the key points when answering questions for revision. Use it as a ticklist to check over the questions when you are Revising. Key words are in italics Contents: 1. Measuring Star Distance 2. The Expanding Universe 3. Tectonic Movements 4. How do we know? 5. Wegener s Ideas 6. Earth Structure 7. Radiation Model 8. The Electromagnetic Spectrum 9. Increasing intensity 10. Microwaves 11. Dangerous side of the EM Spectrum 12. Sunbathing 13. Greenhouse Effects 14. Changing Carbon 15. Digital and Analogue 16. Reducing Energy consumption 17. Nuclear Controversies 18. New Energy resources 19. Renewable vs Non-renewable 20. Different Renewables
How can we measure the distance to stars? How do we know that the Universe is expanding? Parallax Using the fact that stars appear to move against a background of distant stars. Use measurements taken at different parts of the Earth s orbit around the Sun. Work out parallax angle Relative Brightness The brighter a star the closer it would be, the dimmer the star the further away. Problems Uncertainties over measurements as the observations are difficult to make accurately. Red Shift Observations of all galaxies indicate that they are moving away from us. The light coming from them is shifted towards the red end of the spectrum. The wavelength has become longer. Expanding The further a galaxy is from Earth the faster it appears to be moving suggesting that space itself is expanding. Evidence that the Universe began with a bigbang about 14 thousand million years ago and is still expanding outwards. How does the movement of tectonic plates cause earthquakes, volcanoes and mountain building? Tectonic plates move slowly, caused by movements in the mantle. Convection currents Destructive plate boundaries subduction produces volcanoes Constructive boundaries sea floor spreading, associated with volcanoes, magma swelling Mountains form when plates move together Earthquakes caused when plates move suddenly at Conservative boundaries. How do we know that tectonic plates are moving? Evidence in rocks folding shows they have been crumpled since their formation. Fossils of animals that would be found in different climates now in rocks in UK Continents would be worn down to sea level by erosion if mountains were not continuously being formed. Seafloor spreading Consequence of movement of the mantle (convection due to heating by the core) Can see pattern in the magnetisation of seafloor rocks on either side of the oceanic ridges. Caused by the periodic reversals of the Earth s magnetic field.
Why were Wegener's ideas rejected at the time yet they are now believed How do we know about the structure of the Earth? Wegener s Theory That the continents may have moved Evidence at the time: Jigsaw fit of continents Similar fossils in different continents Similar rock layers in different continents Why not believed at the time: Continental movement not observable No known mechanism for movement Wegener was an outside to the geological community Other explanations for idea e.g. land bridge Recent discoveries: Magnetic stripes indicating sea floor spreading Sea floor spreading provided evidence of movement Mechanism discovered convection currents in mantle P waves (longitudinal waves) can travel through solids and liquids S-waves (transverse waves) can travel through solids but not liquids. Both produced when there is an earthquake. P waves detected all around the globe, S-waves not detected in the shadow zone. Indicates that there is liquid inside the Earth that the S-waves cannot travel through. When P-waves move through the Earth they change direction indicating the waves are being refracted as they move from a solid to a liquid. What is the radiation model? How can radiation travel from one place to another? Why is the Electromagnetic Spectrum useful to humans? Radiation model The radiation model is when an object affects another some distance away. Transfer of energy but not matter. One object (source) emits radiation Radiation travels outwards from a source and can be reflected, transmitted or absorbed (or a combination of these) Radiation could affect another object (detector) some distance away when absorbed. Energy is transferred in packets called photons. Electromagnetic spectrum is an example of types of radiation Radio used for communication, broadcasting Microwaves used for communication, used for cooking Infra-Red used in remote controls, thermal imaging, optical fibres, security systems Visible Light used for sight, light houses, optical fibres, photography Ultraviolet Sun beds, security markings, disinfecting water X-Rays Looking at broken bones, airport security Gamma Rays Sterilising medical equipment, killing cancer cells
How could you increase the intensity of radiation reaching a place? How do microwaves work safely? All types of the EM Spectrum travel at same speed, however deliver different amount of energy. Energy delivered dependent upon the intensity of the beam. To increase the intensity: - Increase the number of photons - Increase the amount of energy carried by a photon Intensity also decreases with the distance from the source as: - An ever increasing surface area - Partial absorption by the medium travelled through Dangers of microwaves: People are concerned about health risk of low intensity microwaves from communication devices. Microwaves are strongly absorbed by water molecules and cause them to vibrate and heat up. Evidence that this is a concern to human health disputed. Safety Metal case to reflect and absorb microwaves and keep them within Door screen to reflect and absorb microwaves Recommended distance of use for microwave devices Why are some parts of the Electromagnetic Spectrum dangerous and how can we minimise the risks? The high energy part of the EM Spectrum; Ultraviolet, X-rays, Gamma Rays are ionising radiation. They have enough energy to change atoms or molecules, which can then initiate chemical reactions. This is because they have high enough photon energy to remove an electron from an atom or molecule (ionisation) Minimising risk Ultraviolet Use of sun screen lotions X-Rays absorbed by dense materials such as lead or concrete Why do people sunbathe? Benefits Vitamin D production, enhances uptake of Calcium To get a tan Make people feel better Risks Increased risk of skin cancer Increased risk of cataracts Sun stroke Overall Benefits outweigh the risks Gamma Rays Stopped by thick lead
How does the greenhouse effect work and how are humans contributing to it? How have Carbon levels changed over time, what could be the effects in the future? The Earth is surrounded by an atmosphere that allows some of the EM radiation emitted by the Sun to pass through. This radiation warms the Earths surface when absorbed. Some of the radiation is emitted by the Earth, which has a lower principal frequency than that emitted by the Sun. This can pass out into space, however some is reflected back, or absorbed by the atmosphere, causing the temperature of the Earth to warm up. This is the greenhouse effect. The greenhouse gases are Carbon dioxide, water vapour and methane. Humans are adding Carbon dioxide to the atmosphere by: burning increasing amounts of fossil fuels Cutting down forest to clear land Change over time For thousands of years the levels of Carbon dioxide were fairly consistent. There was a balance in the removal of carbon dioxide by photosynthesis and the release of carbon dioxide by respiration. Over the last 200 years the amount of carbon dioxide in the atmosphere has been steadily rising. Effects Impossible to grow food crops in certain areas due to climate change More extreme weather events, due to increased convection and larger amounts of water vapour in the hotter atmosphere. Flooding of low lying land due to rising sea levels, caused by melting continental ice and expansion of water in the oceans. What are the differences between digital and analogue signals? How could the UK's energy consumption be reduced at a personal and national level? Both are transmitted by being superimposed onto a carrier wave. Digital Discontinuous, either 0 or 1. Can recover the signal if affected by noise Analogue Continuous signal Digital Advantages Can recover the signal if affected by noise Information can be stored and processed by computers Personal Energy saving lightbulbs Energy efficient household appliances Insulate houses from energy loss Washing machines at a lower temperature Double glazed windows National Invest in renewable resources that do not release CO2 Public awareness campaigns Taxation on energy wastage Increase availbility of public transport
Why is nuclear power a controversial means of generating electricity? When considering investing in new energy resources what should you consider? Advantages Cheap Reliable, continuous production Produces a lot of energy for low volume of waste Disadvantages Produces ionising dangerous waste products, which can damage living cells and increase the risk of cancer or cell death. Contamination Irradiation Environmental Impact: The land required, whether there are endangered species, habitat loss, pollution Economics: Price of electricity, cost of setup Waste produced: How dangerous is it, how will it be gotten rid of Carbon dioxide emissions: How much produced per kj of electricity Efficiency: How effective is the method of electricity production Power output and lifetime: How long will it last, will it provide enough power. Risk of large scale, catastrophic events Compare the advantages and disadvantages of a renewable and non-renewable energy source. Compare the advantages of different types of renewable resources Non renewable Fossil Fuels: Will run out, release Carbon dioxide when burnt Nuclear: See disadvantages above Advantages: Cheap, continuous reliable source Renewable Choose from: Wind Water (waves, tides, hydroelectricity) Biofuel Solar Geothermal Any suitable advantages or disadvantages Wind Potentially infinite Can be used singularly Water (waves, tides, hydroelectricity) Good for island countries, or those with rivers Potential to generate a lot of electricity Biofuel Cheap and readily available If replaced, can be a long term reliable source Solar Potentially infinite Can be used on individual homes Geothermal Potentially infinite supply Used successfully in New Zealand and Iceland