P2 – Radiation and Life
By Mr Strugnell
Electromagnetic Spectrum
Warming Ionising
All Radiation
• Travels at the same speed in a vacuum– Speed of light, 3 x 108m/s
• They are all emitted from sources• They can all be reflected, transmitted or absorbed
• They all transfer energy • A packet of EM radiation is known as a photon
Energy and effect
• The higher frequency end has lots of energy and causes ionisation.
• Ionisation is the breaking of atoms or molecules.
• Ionising radiation is:– Gamma– X‐rays– UV
Energy and effect
• The lower frequency side of the spectrum has less energy.
• These cause a warming effect• This is when the energy transferred causes the atoms of molecules to vibrate more.
• This part of the spectrum is:– Radio– Microwaves– Infra Red
Intensity
• Intensity is the amount of radiation arriving in an area.
• Amount of radiation means number of photons
• It increases with distance
Why is this important
• We use radiation for different things.• Microwaves we use in mobile phones and cooking
• Radios are used in communication• X‐rays and Gamma radiation are used in medicine
• IR and UV are used to see heat and at night
Dangers?
• Microwaves heat water molecules, mobile phones are next to your head and your brain is full of water.
• UV radiation causes sunburn• X‐rays can cause cancers as they ionise DNA• Gamma radiation can cause cancers as they ionise DNA
Making them safe
• Your skull absorbs microwaves• You can only have a set number of X‐rays a year and the staff stand outside the room and have protective clothing
• Gamma radiation sources are tightly controlled• You can wear sunscreen of clothes to protect from the sun
• The Ozone layer protects full large parts of the spectrum
Greenhouse effect
• Greenhouse effect is an essential process for life to survive on Earth
• Without our atmosphere and the greenhouse effect it would be very hot during the day 150oC and ‐100oC at night
• DO NOT CONFUSE THIS WITH Enhanced greenhouse effect or global warming.
Greenhouse effect
• IR radiation is trapped within certain molecules in our atmosphere:– CO2 Carbon Dioxide– H2O Water– CH4 Methane
• This means the energy that it transferred is trapped and heat is just energy
Global Warming
• Is the process by which more of these gases are in the atmosphere, which means that more than the normal amount of energy is being trapped.
• This increases the amount of energy which raises temperatures.
• HOWEVER the more amount of energy causes more extreme weather condition, for example colder in the winter.
Carbon Cycle
Communication
• Electromagnetic radiation is used in communications:– Radio waves for radio– Microwaves for mobile phones– Visible light and infra red in fibre optics
Signals
Digital Analogue• Digital has two values 0 and 1• Analogues can have any number over the range
Analogue to Digital
• All signals were in analogue• We knew digital was better because of the effect of ‘noise’
• We didn’t have the technology to encode and decode digital signals
• So we used analogue• We now do have the technology so we have switched to digital
Noise
Digital only looks for 1 or 0 so noise can be easily taken out. It cannot be with analogue
Storage
• Recall that the amount of information needed to store an image or sound is measured in bytes (B)
• Understand that, generally, the more information stored the higher the quality of the sound or image
• Understand that an advantage of using digital signals is that the information can be stored and processed by computers.
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