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Electromagnetic Radiation Light is type of EM radiation Radiation if transfer of energy Visible light just the radiation our eyes can detect 7 Types of radiation: Radio waves, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, Gamma rays Em radiation transfer energy in photons Photons little droplets of energy Sort of like very fine shower Certain types of EM radiation transfer more energy than others Each photon carries energy but not all carry same amount depending on frequency of radiation Frequency depends on where the radiation is on the scale Radio waves have least frequency meaning photons carry less energy compared to Gamma rays

EM Radiation and Energy EM radiation comes from source Lots of things emit EM radiation like sun Frequency of thermal radiation increases with temperature Once emitted EM radiation in vacuum at speed of light 3 things can happen to the energy: Absorbed: like sunbather, absorbing UV rays Reflected: bounces back, like light being reflected from a mirror Transmitted: Just keeps going, like light going through glass What happens depends on substance and type of radiation More than one thing can happen can be transmitted and absorbed Things that absorb radiation called detectors Intensity decreases as distance from source increases When matter absorbs energy, photons transfer their energy Energy deposited depends on number of photons and energy of each photon Intensity= how much energy arrives at each square meter of surface per second W/m2 Intensity decrease with distance because beam spreads out and parts of it get absorbed on the way

Ionisation ALL substances made of atoms and molecules Some types of radiation strong enough to knock out electron and ionize the atom or molecule This can initiate other chemical reactions to take place Takes lots of energy to knock out electron- only Ultra violet and the ones above can ionize. Called ionising radiation Exposure to radiation can kill you If ionising radiation gets exposed to your body cells, then it can damage the DNA and cause it to keep on dividing and dividing which is cancer VERY high doses of radiation can kill you, it's called radiation sickness Light has UV in it which is ionising, overexposure can cause sunburn or skin cancer Longer you're exposed the more intense the damage Protection: UV -very easy to protect yourself from, bu using physical barriers, like sun cream and clothes X-Rays- Lead aprons used and lead shields. Also doctors stand behind concrete to protect themselves

Uses of EM Radiation EM radiation can cause heating Some types of EM radiation don't have enough energy to change atoms but they transfer energy to the atom/molecule and heats them up This heating effect can cause damage to living skin cells like when you burn yourself This effect can be useful though because it used in heating up food. Normal ovens use infrared and microwaves use microwaves Microwaves strongly absorbed by water molecules making it good to heat up food because all food has water in it Can be dangerous because microwaves could heat up water in cells in your body but they have protective layers on the doors meaning the microwaves get reflected back into the microwave Higher the rating on microwaves the quicker it will cook your food Phones emit microwaves so when you call on the phone, the waves could potentially heat up cells in the body and tissues like the brain Could lead to cancer Not enough evidence yet to come up with full conclusion Phone masts also emit microwaves meaning people living near by could be affected by these waves

EM Radiation and the Atmosphere Earths atmosphere protects us from harmful radiation Absorbs and reflects it back Some of it gets through though Sun emits radiation and reaches to Earth and Earth absorbs it Warms it up Earth emits some EM radiation back Cools it down EM radiation then absorbed by green-house gases which re re radiate heat all over the place keeping earth warm at night Too much though can cause global warming Ozone layer protects us from UV radiation Ozone form of oxygen made at certain height in atmosphere UV breaks O2 molecule and then single molecule goes and joins another O2 making O3 Reaction keeps on going meaning it's reversible Ozone protects from UV radiation which is ionising Loss of ozone would create holes and means we get harmed Ozone VERY important

Carbon Cycle Carbon over thousands of years has mainly been constant The cycle keeps it in a constant amount Respiration in plants and animals and in decomposers increase of CO2 Photosynthesis increase it Recently (last 200 years) humans messing up the balance More CO2 being released More cars, electrical goods being used Means more energy used Also population rising meaning more land needed More trees being chopped- less photosynthesis More trees being burnt- more CO2 being made

Global Warming and Climate Change Been evidence that our increase of use of fossil fuels has increased CO2 levels Global temp risen Lots of evidence to show rise in CO2 causing rise in temp Now scientific agreement that humans cause of global warming Climate models can help us understand the climate change Global warming causes sea level rises because when seas gets hotter it expands Ice caps melt as well increasing sea level more More hurricanes, floods, winds Longer droughts in certain places Change in weather patterns also affects food production

EM Waves and Communication Em radiation been used for communication for years now Infrared- TV remote controls Microwaves- Phones Radio waves- TV and radio Radio waves and microwaves good at transmitting because atmosphere doesn't absorb them as much as the other radiations Radio waves used for TV have short wavelengths compared to most radio waves Microwaves used for phones have long wavelengths compared to normal microwaves Microwaves are used for satellite communication Signal from transmitter transmitted into space then absorbed by satellite receiver Then sent back down to Earth in different direction and received by satellite dish Infrared and light used in optical fibres Waves go in one end and bounce off sides of thin inner core of glass/ plastic until reaches to other end

Analogue and Digital Signals Information being sent is converted into electrical signals before being transmitted Sent long distances down telephone lines or superimposed onto carrier EM waves Then sent as digital or analogue signals Analogue signals vary but digital are on or off Both signals weaken through travel so amplifying fixes this problem Digital are better quality When there is a disturbance it's easy to fix it with digital because theres only 2 values But for analogue it's hard to tell the original look Also with digital technology you can transmit more than one signal at once

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