Core Physics - Topic 2 Electromagnetic Spectrum 4.0 / 5 based on 2 ratings ? PhysicsElectromagnetic SpectrumGCSEEdexcel Created by: KatieCreated on: 10-04-13 19:04 Beyond The Visible William Hershel (1738-1822) Different coloured filters heated up his telescope to different extents Did different colours of light contained different 'amounts of heat'? Split sunlight into a spectrum using a pyramid Put a themometer at each colour & saw temperature rise Measured beyond the red end of the spectrum no visible light highest temperature of all INFRARED waves/radiation Johann Ritter (1776-1810) aimed to find 'invisible rays' at the violet end of the spectrum used silver chloride chemical turned black fastest when exposed to 'invisible rays' beyond violet ULTRAVIOLET waves/radiation Electromagnetic radiation - visible light, infrared and ultraviolet Transfer energy from one place to another Electromagnet vibrations are right angled to the direction of the waves - traverse waves 1 of 5 The Electromagnetic Spectrum Electromagnetic waves travel without any particles to vibrate Move easily through a vacuum e.g. space Travel at 300,000 km/s in a vacuum fastest speed anything can come Colour of visible light depends on wavelength Light waves longer than red lights - humans can't see e.g. infrared, microwaves and radiowaves Shorter wave lengths mean high frequencies higher frequency than visible light e.g. ultraviolet, X rays and gamma rays The Hubble Space telescope detects visible light, UV and IR Radio and X-ray astronomy have developed relatively recently 2 of 5 Electromagnetic Dangers Mobile phones use microwaves but at a different frequencies to microwave ovens scientists say mobile phone use doesn't cause a health risk Microwave ovens use a certain frequency that heats water danger to humans because our bodies are mainly water IR radiation used in grills and toasters to cook food Our skin absorbs IR which we feel as heat too much can destroy cells causing burns to skin Higher frequency transfer more energy - more dangerous Sunlight contains UV - carries more energy than visible radiation UV transferring to our cells can damage their DNA can damage skin cells so much that it can lead to skin cancer UV can also damage our eyes skiers/mountaineers suffer from temporary 'snow blindness' X-rays and gamma rays can penetrate the body excessive exposure may cause mutations in DNA killing cells and causing cancer 3 of 5 Using Electromagnetic Radiation EURion pattern on banknotes can be seen when illuminated reflect certain wavelengths of visible light Security markings on banknotes can't always been seen fluorescence absorbs UV light and re-emit visible light Fluorescent lamps produce UV waves, use a fluorescent material inside X-ray scanners used in airports to detect hidden objects All warm objects give off some heat as IR radiation Radiowaves and microwaves carry TV signals Radiowaves carry Wi-Fi signals Microwaves carry mobile phone signals IR waves carry short distance signals like remote to TV IR waves sent down optical fibre cables for telephone and internet UV light kills bacteria - disinfect water and sewage Gamma rays kill cells - used to sterilise Gamma rays detect and kill cancer cells in radiotherapy chemical that emits gamma rays injected into the blood collects inside cancer cells and are decteted and located by a scanner 4 of 5 Ionising Radiation Gamma rays increase cancer risk by causing mutations to cell's DNA because they are ionising radiation Ionising radiation can remove electrons from atoms to form ions ions are very chemically reactive DNA damage if atoms in the cell are ionised More exposure = more destroyed cells Elements like radium naturally emit gamma waves therefore radioactive Some radioactive substances emit alpha and beta particles All types of ionising radiation transfer energy from the radioactive material to surroundings Alpha and beta particles are not electromagnetic radiation They are particles of matter that are emitted with lots of kinetic energy the energy can ionise atoms So they are also potentially hazardous to life and damage DNA in cells 5 of 5
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