P2: Radiation and Life

P2: Radiation and Life

1. Electromagnetic Radiation

   • 7 types of radiation
     • Radio Waves
       • Non-ionising
       • Least penetrating
       • Low energy and frequency
       • Long wavelength
       • used to transmit television signals and radio programmes since they have a long wavelength
         • it can lead to cancer and other disorders
         • affects people's health if power cables are too close to their homes- low frequency fields
     • Gamma Ray
       • High frequency and energy
       • Short wavelength
       • Most penetrating
       • Ionising
       • Uses
         • used to kill cancer cells and sterilise medical equipment/ food
     • Ultraviolet Rays
       • used in shops to detected forged bank notes-they absorb the chemicals found in the bank notes and change clour
       • used to kill microbes and sterilise equipment
     • X-rays
       • used to produce photographs of the bones inside the body because the rays are absorbed by dense materials
       • ionising
     • VisibleLight
     • Infrared waves
       • used in thermal imaging cameras/mobile phone cameras/ remote controls for TVs
         • overheating can cause skin burns
     • Microwaves
       • Makes particles vibrate, which heats them up. Some waves are absorbed by water molecule and so can heat things up containing water ( there is water in all food substances)
       • more powerful ovens produce higher intensity radiation, so less time is needed to produce the same heating effect
       • metal cases and screens protect the waves from escaping by reflecting and absorbing the waves ( if you are exposed to the waves, water particles in the body could heat up
       • used in mobile phones to send signal, however it could be dangerous as the phone emits microwave radiation
   • Transferring Energy
     • heat energy travels through space as infrared radiation
     • energy is delivered as photons (packets of energy)
     • the intensity of electromagnetic radiation is the energy transferred per second per metre square ( W/m square)
       • not all photons carry the same amount of energy
       • amount of energy delivered to a receiver depends on the number of photons that arrive and the type of photons (type of radiation-frequency)/ how much energy each photon carries
         • TOTAL ENERGY=number of photons x energy of each photon
       • as the distance from the source increases, the intensity of light decreases because less photons are reaching the detector( beam spreds out and it id partially absorbed)
     • Speed of light is 300 000km/s
   • Things that can happen to radiation
     • Reflected: bounce back, like light reflected from a mirror
     • Transmitted: just keep going, like light passes through glass
     • Absorbed: like a sunbather absorbing UV rays from the Sun

2. Ionisation

   • All substances are made of atoms and molecules. When a photon hit an atom or molecule, it sometimes has enough energy to remove an electron and change the atom or molecule
     • this can initiate other chemical reactions
     • only gamma rays, X-rays and ultraviolet waves can cause ionisation since they have enough photon energy
   • in the cells of the body there are many important molecules, including the DNA, which contain instructions for the cell and are important in cell division.
     • if these cells are exposed to ionising radiation, the damage to DNA molecules can cause mutations, and the cells might start dividing over and over again- leads to cancer
       • very high doses of radiation can kill the cells altogether- radiation sickness
   • UV radiation damages living cells in the skin-leads to sunburn or skin cancer
   • Protection
     • X-rays: lead shield over parts of the body that are not investigated when taking a radiography. The lead absorbs the rays. Rdiographers wear lead aprons or stand behind concrete.
     • UV radiation: physical barriers such as clothes or sunscreen

3. Signals

   • Analogue
     • continuous electric signals (frequency and amplitude vary continuously)- can have any value within a particular range
     • it is cheap and it can be portable
     • infinite amount of data
     • higher density-it can carry more refined information
     • lower quality than digital signals
     • affected by noise, which means that the data is less accurte and signals are lost (hard to process
     • less efficient than digital signals as they carry less information per second
     • recorded by a microphone in the telephone which converts them into electric vibrations, and hence they can be read as electric signals ( the microphone does this by sensing how the air pressure varies from one moment to anther generating an output voltage power). After that the patter is transmitted through wires to the loudspeaker in the other telephone over the telephone lines.
   • Digital
     • can only take one of a small number of discrete values (usually two)
       • carried by switching the Em carrier wave on and off- this creates pulseswhich are decoded by a digital receiver to get a copy of the original signal
     • more efficient as tehy carry more information per second than analogue signals using just one cable
     • higher quality since the information received is the same as the original and it is not affected by noise
     • easy to process and decode- using computers which are digital devices
     • data can become corrupt or lost as computers are not reliable sources to use bcause they crash
     • difficult to understand-complex
     • sound quality can be lost
   • information is converted into electrical signals before it is transmittes
   • Optical fibres work by bouncing waves off the sides of a thin inner core of glass or plastic. The wave enters one end of the fibre and is reflected repeatedly until it emerges at the other end
   • radio waves and microwaves are good at transmitting information over long distances because they don't get absorbed by the Earth's atmosphere as much as most waves in the middle of the EM spectre

4. The Carbon Cycle

   • Process that return carbon dioxide in the atmosphere
     • respiration in plants and animals
     • respiration in decomposers-when plants and animals die, decomposers break them down. As they do they respire.
     • burning fossil fuels
   • Photosynthesis in green plants and other organisms remove carbon dioxide from the atmosphere
   • an increase of the carbon dioxide level in the atmosphere lead to global warming
     • more extreme weather
     • ice melting causing sea level rise
     • animals and plants lose natural habitats and may become exinct