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Slide 1

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Keywords:Electromagnetic radiation, reflected, absorbed, transmitted, wavelength,
Analogue and digital signals
Infra red and visible light
analogue signals
continually vary Can send signals down optical fibres
and so travel in curved paths
digital signals are either
on or off (good for
computers, less prone to
Electromagnetic Radiation interference)
Waves move energy they can be reflected, transmitted or absorbed. can pass through
When absorbed it: makes the substance hotter Gamma, x-rays, ultraviolet Earth's atmosphere and
Gamma and x-rays mainly pass are used to send
may create an alternating current with the same frequency as through soft tissue. signals too and from satellites
the radiation Large doses can kill cells, small doses
can cause cancer
Wave speed
Big Bang Theory
Wave speed (v) = frequency (f) x wavelength ()
The further away a galaxy is the
in m/s in Hz in m
bigger the redshift, therefore the
All electromagnetic waves travel at 300,000,000 m/s in a vacuum faster the galaxy is moving away.
This shows the universe is
Red shift and doppler effect expanding
Observations are made using telescopes on earth that detect light, radio
and x-rays. Easy to fix but not all e.m waves reach earth.
If something is moving away it's
wavelength becomes longer, and
frequency lower. For light it shifts to the
red end of the spectrum
in space all e.m.waves can be detected using
satellites. The atmosphere does not get in the way but this is
very expensive
This supports the big bang theory
that the universe started from a
single point 15 billion years ago
Keywords: communication,analogue, digital, frequency, gamma, ionising, red-shift, big bang.…read more

Slide 2

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Keywords: radiation, half-life, proton, neutron, electron, isotope, alpha, beta, gamma
Structure of the atom Nuclear radiation Thickness control half life
deflected in
magnetic and electric fields
helium nucleus
deflected in
PROTON ­ positive, same magnetic and electric fields
mass as neutron ("1") electron
neutral, same ELECTRON ­ negative, mass
mass as proton nearly nothing Not deflected
("1") e.m. wave
Beta radiation
Half ­ life
Time it takes for number of radioactive nuclei/count
rate to fall to half its initial value Tracers half life hours
it 100
5 1
Half lives T 2 3 4 Time
T T 0 T (s)
Isotopes Gamma radiation
Penetrating power
Smoke Alarms ­ half life years
In air :
- 5cm
- 1m
- km
Ionising power
Alpha ­ very
Alpha radiation
Gamma - weakly
Keywords: ionising, penetration, range, tracer…read more


Anisa -Team GR


Saloni Shah


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