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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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