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Physics 2 ­ Radiation and Life
GCSE Level
OCR 21st Century Science
By Izzie Sims…read more

Slide 2

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Electromagnetic Radiation
· Light is a type of electromagnetic
radiation. Radiation means a transfer of How to Remember the
energy. For example sunlight is a transfer Different Types of Radiation:
of energy from the sun to the earth.
· There are seven types of radiation
altogether, making up the
electromagnetic spectrum…read more

Slide 3

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Electromagnetic Radiation
Visible light is the only part of the spectrum we can see but all types of
electromagnetic radiation transfer energy. For example you can feel warmth
from the sun because heat energy is travelling through space as infra-red
The energy is transferred as
photons. A photon is a tiny
`packet' of energy. The
amount of energy that a
photon carries depends on
the type of radiation. The
amount of energy
increases as you go down
the spectrum, so Gamma
rays have the most and radio
waves have the least.…read more

Slide 4

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EM Radiation and Energy
When radiation is emitted from a source it spreads out until it hits something,
i.e. glass, walls or a person. Three things can happen:
·The radiation is transmitted, so it keeps going.
· It's reflected or bounced back
· It gets absorbed, for example sunbathers absorb UV radiation from the
When radiation is absorbed, the photons transfer
their energy to the mater. The intensity of a
beam of radiation decreases with distance
from the source. For example if you are
standing next to a fire you will feel warm, but if
you move away you will feel colder because fewer
photons will be reaching you.…read more

Slide 5

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· High energy EM Radiation is more harmful than low energy radiation .
All substances are made from atoms. When a photon hits an atom it
sometimes transfers enough energy to break up the atom into bits called
ions. This process is ionisation. Only high energy radiation does this, UV, X-
rays and gamma rays.
· There are some molecules in your body that DO NOT want to have a lot
exposure to ionising radiation. Like DNA molecules. Very high doses of
radiation can kill cells altogether or cause mutations. In the case of a
mutation, the cells might start dividing too fast without stopping which is called
· To protect ourselves against UV rays we wear clothes and suns. If you
have to have an x-ray taken, the radiographer will put lead shields over the
parts of your body that aren't being x-rayed and stand behind a lead screen.
Lead absorbs X-rays so you aren't unnecessarily exposed.…read more

Slide 6

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EM Radiation and Life
Radiation makes pretty much all life possible. Nearly all life on earth relies on
EM radiation from the sun. This radiation does two things:
· Keeps the planet warm during the day. The earth's surface absorbs radiation
and warms up.
· Provides energy for photosynthesis (the process by which green plants
make food.)
So no sunlight = no life. The planet would be too cold for anything to live on and
there'd be no photosynthesis so there would be nothing to eat.
=…read more

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