P2 - Radiation and Life

P2 - Radiation and Life

1. The electromagnetic spectrum.

   • Gamma Rays
     • Used for treating cancer, sterilising medical equipment, killing harmful bacteria.
   • X Rays
     • Used for taking x ray photos, examining crystals. Can cause cancer.
   • Ultra-violet light.
     • Used for tanning beds, lamps, fluorescent bulbs, and security purposes. Can cause skin cancer.
   • Visible light.
     • Used for seeing (obviously), telescopes, microscopes, endoscopes, optical fibre communications.
   • Infrared
     • Used for night vision, TV removes, toasters, grills, police detection, and heaters.
   • Microwaves
     • Used for satellites and microwaves. Can damage tissue.
   • Radiowaves
     • Used for communication, remove controlled vehicles, TV, radio.

2. Information about radiation.

   • Electromagnetic radiation is emmitted from a source.
     • When radiation is emitted from a source, it spreads out until it reaches some matter. Three things can then happen.
       • It can be transmitted. This is where it just passes through the matter.
       • It can be reflected. This is where it bounces off the matter.
       • It can be absorbed. This is when the radiation is taken in.
         • When radiation is absorbed, the photons transfer their energy.
   • All EM radiation travels through a vacuum at the same speed.
     • This speed is the speed of light, about 300,000 Km/S
   • The intensity of radiation means how much energy arrives at each square metre of surface per second. The units of intensity are W/m2
     • Beam intensity decreases as distance from source increases. This is because...
       • The beam spreads out.
       • The beam gets partially absorbed.
   • Ionisation.
     • When a photon hits an atom or molecule, it can have enough energy to knock off an electron.
     • Gamma rays, X Rays and UV light are ionising radiations.
     • Ionising radiations can be very dangerous within the body.
       • If cells are exposed to this, the damage to DNA molecules can cause mutations. This can cause cancer.
         • Very high doses can kill cells.
     • X Rays
       • X Rays are used because they pass through flesh but are absorbed by denser materials such as bone.
         • This is why they are also used for security purposes.
         • Some radiographers may use lead shields to protect other parts of the body.
   • Non-ionising radiations.
     • They don't have the energy to change atoms.
     • However, when non-ionising radiations are absorbed, they transfer energy. This creates a heating effect.
       • Microwaves make particles vibrate, which heats them up.
     • Microwaves with a higher power rating produce a higher intensity of radiation.
     • Microwave radiation heats up water in cells.
     • Microwaves are used to send signals between mobile phones and mobile phone masts. This is because they can reach satellites in geostationary orbit, and they are non-ionising.
       • However the radiation used for these phones could cause heating of body tissues.
       • There are risks that this could cause cancers.
       • However, we will not know the full effects for many years.

3. The atmosphere.

   • The gases in the atmosphere filter out certain types of radiation from the sun.
     • However, visible light and radiowaves can get through. This is why we use them for communications.
   • The Greenhouse Effect
     • The Greenhouse effect regulates the Earth's temperature.
     • • 1. Electromagnetic radiation from the sun passes through the atmossphere.
       • 2. The Earth absorbs the radiation, and so warms up. Some of the waves are emitted back in to space.
       • 3. Much of the radiation is absorbed by atmospheric gases, which reradiate heat in all directions.
       • 4. Some of this heat goes back towards Earth.
   • Hole in the ozone layer.
     • Ozone is a form of oxygen - three oxygen molecules joined together. O3.
       • When it absorbs UV light, it splits in to O and O2.
     • The ozone layer is very important. It protects us from too much UV.
     • We have created a problem with synthetic materials called CFCs. These are often found in fridges. However, when they escape in to the atmosphere, ozone becomes ordinary oxygen.
       • Over time, this has left a hole in the ozone layer, meaning more UV can reach Earth.
         • To fix this, we are removing CFCs from aerosols and old fridges.
   • The carbon cycle.
     • • Respiration in plants and animals, respiration in decomposers, and burning, return CO2 to the atmosphere.
       • Photosynthesis removes CO2 from the atmosphere.
       • For thousands of years, the process has remained balanced, and the levels of CO2 have remained constant.
         • However, people's lifestyles have changed, and we are now putting in more CO2 than we are taking out.
       • People's lifestyles have changed - we use more vehicles and gadgets, so more CO2 is produced in providing energy.
       • The population is also increasing, meaning more space is required for houses and food. This means chopping down trees and burning them. This also releases CO2 because it is not being used for photosynthesis.
       • There is a link between CO2 levels and temperature. This is because the greenhouse effect is increasing.
       • Global warming.
         • Global warming is serious. As the sea gets warmer it expands, causing sea level to rise. People living in low lying places risk their homes being flooded.
           • Higher temperatures also make ice melt, causing seas to rise.
         • Global warming has changed weather patterns. Regions will suffer more extreme weather such as longer, hotter drought. Hurricanes form when water is over 27 degrees. Extra heat will increase convection, so stronger winds. More water vapour, more rain.
           • Changing weather patterns will effect food production.

4. Waves

Images and files in the map