P2 Flashcards
How does a beam of electromagnetic waves transfer energy in?
Electromagnetic waves transfer energy in packets called photons
How do you increase the energy of a photon?
You increase the frequency of the electromagnetic wave which increases the energy of its photons
What are the electromagnetic radiations in order?
Radio waves micro waves infrared visible light ultraviolet X-rays gamma rays
increasing frequency, decreasing wavelength
How do you measure the intensity of a beam of electromagnetic radiation?
You measure the energy driving at a square meter of a surface each second
What does the intensity of a beam of electromagnetic wave depend on?
the number of photons per second (increase photons, increase intensity)
the energy transferred by each photon
What is ionisation?
Some ionising radiation like X-rays and gamma rays have enough photon energy to knock off electrons in an atom. An atom is ionised when it loses electrons. It can start off a chemical reaction in solving the ionised atom.
How do you increase the thermal energy transferred from radiation?
You increase its exposure time and intensity.
How do microwaves heat things?
As water molecules absorb microwaves and they vibrate more and share this energy with other molecules around them, they can heat up food that contains water
How are we protected from the radiation from microwave?
The microwaves reflect off the metal in the walls and door and are absorbed by cells instead of escaping
How does Ozone layer protect us from ultraviolet radiation and its effects?
Ozone is O3 molecule and absorbs ultraviolet radiation from the sun however CFC’s are causing the Ozone layer to become thinner and more holes to appear
What protects us from the effects of ultraviolet radiation?
Ozone layer
Sunscreen
Clothes
What is the greenhouse effect?
Radiation from the sun contains a lot of frequency’s
The Earth’s atmosphere lets some of the sun’s radiation in
the radiation is absorbed by the Earth’s atmosphere which warms it
Radiation emitted by the earth cools it down and can pass into space reflect off clouds or reflected off some gases in the atmosphere keeping the Earth warm, this is called the greenhouse effect
What are three greenhouse asses in the atmosphere?
Carbon dioxide
Methane
Water Vapour
Why has the level of carbon dioxide in the air been the same for many years?
The rate of absorption and release of carbon dioxide have been the same
Why has the level of carbon dioxide in the atmosphere increased?
Burning of fossil fuels has increased the rate of release of carbon dioxide in the atmosphere
Cutting down forests (deforestation) has decreased the rate of absorption of carbon dioxide
what do computer climate models suggest?
extreme weather
- increased water vapour in the hotter atmosphere
- increased convection increasing wind speed
What can global warming result in?
-impossible to grow food crops in some regions
-more extreme weather because of increased level of water vapour in hotter atmosphere and increased connection
increasing the wind speed
-flooding of low lying land due to rise in sea levels as glaciers melt and water in oceans expand
Why can some electromagnetic frequencies be used to transmit information?
Infrared and light can be used for long distance telephone and internet communication because they are not absorbed by the glass of optic fibres
Radio waves and microwaves are not absorbed by air so they can carry tv and radio broadcasts through the atmosphere
What is a carrier wave?
Radio waves use carrier waves to transmit information
What is modulation?
It is a process used to change the amplitude or frequency of the carrier
What are analogue signals?
They are signals that vary continuously
What are digital signals
They are signals that can only take a small amount of discrete values usually two, called 0 and 1
What are the advantage of digital signals over analogue signals
- Radio waves can be affected by noise, noise changes amplitude and reduces the quality of a signal of a analogue signal because the original sound cannot be separated by the noise whereas in digital signals it can, quality not affected
- Easily stored in electric memory so can be processed by computers
- Digital signals carry more information
- More data
