1. The document discusses electromagnetic radiation and its various uses including communication technologies like radio, TV, and WiFi. 2. It explains how different types of electromagnetic radiation such as infrared, microwaves, and radio waves are used to transmit information over long distances. 3. The document also covers topics like how digital signals make communication more robust than analog by sending information as discrete pulses rather than continuous waves.

1. P2 Radiation and Life
REVISION NOTES BASED ON COLLINS NEW
GCSE SCIENCE AND ADDITIONAL SCIENCE
Sig’s School Work Help

2. Electromagnetic Spectrum
T.V & Radio
waves
Microwaves Infrared
V
I
S
A
B
L
E
Ultra Violet X-Ray Gamma
Increasing wavelength
Energy increases
&
Frequency increases ALL:
• Travel at speed of light in a
vacuum
• Emit Electromagnetic Radiation
If you want, find some examples of
items that use these types of
radiation

3. Intensity
Energy per second
XIntensity Area
Intensity = Energy per Second Add these units to your answer: J/S/M² or W/M²
Area
(that photons are falling on)
Joules per Second per Metre squared
Watts per Metre squared
The intensity of a beam of radiation depends on:
• The energy of the photons – the type of radiation
• The number of photons per second
• The area with which the photons are colliding

4. Ionisation
Ultra violet, X-rays and Gamma radiation can create ions because they have so
much energy
• If ions are created in our cells, this can cause them to reproduce abnormally
and they may form a tumour
• If the tumour is cancerous it can be very dangerous
• Although some gamma radiation can cause cancer, in high doses it can be
used to kill/exterminate cancer cells

5. Energy Diagrams - Scientific
• P= Current x
Voltage
Or
• P= Energy
time
• Unit= kw x h
• Units for
Power= Watts
of J/S
Power is the rate at which energy is converted
Power = Energy
Time
Energy (J)
X
Power (W or J/S) Time (S)
Electrical Power = Current x Voltage
Power (J/S or W)
XCurrent (A) Voltage (V)

6. Energy Diagrams –Calculating Energy
• P= Current x
Voltage
Or
• P= Energy
time
• Unit= kw x h
• Units for
Power= Watts
of J/S
Energy (J)
XPower
(kW)
Time
(Hour)
Energy = Power x Time
= kilowatts x Hours
So when paying for electricity we calculate
the power in kilowatts and the time in hours
1 kW = 1000 W
E.g.
A 5000W motor running for 3 hours uses:
5 kW x 3 Hours = 15 units/h
or
15 kW/h

7. Sankey Diagrams
A Sankey Diagram shows how energy is converted to different types in a system.
We always assume that energy is conserved (the total energy input is the same as the energy output).
1000J
300J
150J
50J
500J

8. Microwaves
How they work:
The oven generates microwaves, which are
directed at the food. Water molecules in the food
absorb the photons. This causes the molecules to
vibrate and they pass on their vibrations to other
water molecules. In this way heat is conducted
throughout the food.
In order to protect us from microwave
radiation, the ovens have metal casing to reflect
the photons back into the oven and a metal mesh
in the glass part of the door, which also reflects
the radiation.
Mobile Phones:
Mobile phone networks use low intensity
microwaves. The heating effect of these
microwaves is very small but some people are
concerned about the health risks from the
radiation; the risk of cell damage from mobile
phones is measured by comparing cancer rates
in large groups of people who do and do not
use mobile phones.
There is no evidence of
harm from mobile
phone use

9. Ozone
• Ozone is a form of oxygen found in the outer layers of our atmosphere, which absorbs ultraviolet rays from the
sun (only radiation absorbed by ozone)
• Ultraviolet radiation causes sunburn and can lead to skin cancer and eye damage to the retina
• Chemicals containing CFC’s (Chlorofluorocarbons) were invented with many uses including refrigeration, aero-
sols and fire-fighting; about 50 years ago, researchers realised that these chemicals /CFC’s were damaging
the ozone layer due to the break down of the ozone molecule
• When a photon of ultraviolet radiation meets an ozone molecule, all its energy is absorbed in splitting the
molecule. The molecule then reforms to absorb the next photon. This is how the ozone layer protects us
O
O O
Ozone is O³

10. • The sun emits different frequencies of
electromagnetic radiation. This radiation reaches
the Earth’s atmosphere
• The Earth’s atmosphere reflects some of this
radiation back to space
• The Earth’s atmosphere transmits some of this
radiation to the Earth’s surface
• The Earth’s surface absorbs radiation that
reaches it, and it warms up. Because the Earth’s
surface is warmer it emits more electromagnetic
radiation
• The Earth’s atmosphere reflects some radiation
back to the Earth’s surface
• The Earth’s atmosphere absorbs some radiation
and re-radiates it back to earth
• The Earth’s atmosphere transmits some radiation
back to space
• The Earth and its atmosphere become warmer if
more radiation is absorbed than emitted
Greenhouse Effect
The main greenhouse gases are
• Methane
• Carbon dioxide
• Water vapour
The principle frequency of that radiation is the one with greatest
intensity; increases with increasing temperature
Radiation from the hot Sun has a higher frequency than radiation
from the cool earth

11. Global Warming
• The greenhouse effect is slowly increasing the average temperature worldwide. This is called global
warming
• Global warming will have many effects including:
• Changes to the crops which can grow in a region
• Flooding of low-lying land due to rises of sea level as the sea expands and glaciers melt
• Various gases in the atmosphere are responsible for the greenhouse effect:
• Water vapour has the most effect, because there is so much of it
• The small amount of carbon dioxide has an affect
• Methane is a strong absorber of infrared radiation; there is very little of it
• Scientists use computer models to predict the effects of global warming. The models are tested by seeing
if they can use past data to predict today’s climate
• Models suggest that global warming will result in more extreme weather events because of:
• Increased water vapour in the hotter atmosphere
• Increased convection in the atmosphere increasing wind speed

12. • Carbon Dioxide is one of the main greenhouse gases
found in the Earth’s atmosphere
• The level of Carbon Dioxide in the atmosphere has been
steady for thousands of years, because the rates of
absorption and release of Carbon Dioxide have been the
same
• But, in the last 200 years the levels have steadily
increased due to:
• The burning of fossil fuels as an energy source
has increased the rate of release
• Cutting down forests (deforestation) to clear
land has decreased the rate of absorption
• The recent increase in the temperature of the Earth
correlates with the rise in Carbon Dioxide levels in the
Earth’s atmosphere. Many scientists believe that this
correlation is caused by the Carbon Dioxide because it is
a greenhouse gas
CO² in the atmosphere

13. Electromagnetic Waves For Communication
Waves that carry information:
• Conversations, music, pictures and other
information can be carried from place to place
using electromagnetic waves
• The main types of radiation used for
communication are radio wave, infrared
radiation and visible light Microwaves can
pass through the
atmosphere to
satellites but longer
wavelength radio
waves are reflected
Radio Waves Microwaves Infrared
Transmit terrestrial T.V. and radio
programmes from a transmitter to a
receiver; the waves are not strongly
absorbed by air so they can travel many
kilometres and are able to spread
around hills, buildings but also reflect
off layers in the atmosphere
Have a shorter wavelength than
radiowaves and are slightly absorbed by
the air.Narrow beams of microwaves
travel many kilometres through the
atmosphere and interact with satellites
Used (in remotes) as it can only travel
short distances in air and cannot pass
through walls, this means that the
remote will not be controlling
another/different T.V.

14. Optical fibres
• Very narrow glass fibres called optical fibres carry
infrared and light signals long distances
• Infrared radiation and visible light are not absorbed much
in glass, repeatedly reflecting off the sides of the glass
fibre
• Optical fibres are used in telephone, internet and T.V.
cables
• More than one signal can pass through an optical fibre at
the same time

15. You tune your radio to a certain frequency to listen to
your favourite radio station; This frequency is the
frequency of the carrier wave. A carrier wave is a
radio wave which carries information from the
broadcasting station to your radio
No programme is broadcast
Information containing the programmes sounds or
images is added to the carrier wave. The carrier wave
is modulated
This creates a signal that is transmitted to your radio
set
Your radio can separate out the modulation from the
carrier, so you can hear the programme
In analogue broadcasting, the signal added to the
carrier wave can vary continuously. This is an analogue
signal. The frequency of the carrier wave and its
amplitude can have any value
How Waves Carry The Information
Carrier Wave
Sound Signal
Carrier wave
modulated by
sound signal

16. Noise is an unwanted signal mixed in with
the signal we want. Since digital signals
consist of a series of steps, it is easier to
separate noise from a digital signal than
from an analogue signal. Also, when an
analogue signal is amplified, the noise gets
amplified as well
Digital VS Analogue Signals
A digital signal is made of a series of discrete
(separate) steps. For example: a normal light
switch, a digital thermometer; has a number of ‘0’
or ‘1’ values
An analogue signal is continuous. For example: A
dimmer switch, a liquid-in-glass thermometer
Storing Digital Information:
• Bit – a binary digit i.e. a ‘O’ or ‘1’
• Byte – 8 bits
• Kilobytes – 1000 bytes
• Megabytes – 1,000,000 bytes
• Gigabyte – 1,000,000,000 bytes
• Pixel – An area of an image. The
smaller the pixels the clearer the image