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Slide 1

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Electromagnetic Energy travels through electromagnetic waves.
· These waves have wavelength, frequency, amplitude and speed.
· All waves travel at the SAME speed.
· Wavelength is the distance for one wave, measured in metres.
· Frequency is how many waves go past you in one second (Hz)
· Wave speed = frequency x wavelength.
· Higher frequency = shorter wavelength.
· There are 7 main parts to the spectrum: radio waves, micro waves,
infra red, visible light, ultra violet, x-rays and gamma rays.
· Radio Waves are used for communication. They transmit through
the atmosphere, buildings and people are transparent to them
(harmless) they have long wave lengths!
· Micro waves are used in cooking and communication. They are
slightly absorbed by humans. (only harmful if high dosage)
· Infrared is used and is given off by warm objects. It is absorbed by
human tissues to a limited depth (pretty harmless)
· Visible Light is found in hot objects like the sun. it is strongly
absorbed at the body temperature but only heats it slightly. Too
much can cause damage to the retina.
· Ultra violet light comes from hot objects. It is absorbed by out
bodies. The shorted wavelength rays can do damage by ionising atoms
in our skin tissues. It can also cause skin cancer!
· X-rays are used in hospitals to take photographs because they can
pass through flesh. It is very dangerous to humans as they penetrate
the skin and absorb into the bone.
· Gamma Rays are radioactive. They through our bodies and most
materials. They can ionise cells, and are a great danger.
· Radioactivity is made up of three main things: alpha, beta and
gamma.…read more

Slide 2

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Alpha particles are helium nuclei and do not penetrate far into materials. They
have a mass of 4 and a charge of +2.
· Beta particles are electrons and they penetrate moderately. They have a mass
of 1 and a charge of -1.
· Gamma Rays are EM waves and they penetrate very deeply. They have a mass
and charge of 0.
· Isotopes are atoms with a different number of neutrons.
· Information such as sounds and pictures are converted into electrical signals, it
is then sent on EM waves. There are two types, analogue and digital.
· Analogue signals vary and the amplitude and frequency can take any value.
However, digital are either on or off, which provides a far better quality of
· Half life is the average time taken for half of the radioactive material present
to decay.
· You need a long half-life for devices that have to last, for instance sterilising
machines have to use gamma rays with a long half life. Also, I smoke detectors
(when alpha is used)
· Beta or gamma is used in medical tracers because they can penetrate the skin,
and get back out. Where as alpha cant once it enters the body!
· There are many theories about the Universe: the big bang, genesis, string
theory and the big crunch.
· Light from other galaxies is being red shifted away. Red shift is when a object
moves away from the light and it moves towards the red part of the spectrum.
· The frequency of galaxies that are moving away have a lower frequency than
that closer.
· A star is formed by dust and gas gathering due to gravity. As the mass
increases, so does the gravity and it starts to get hot. Eventually this triggers a
nuclear explosion and a star is born.
· The death of a small star: when the hydrogen runs out, it expands and becomes
a red giant. (the nuclear reactions stop) this forms a white dwarf and then a
black one.
· The death of a large star: the hydrogen runs out and a red super giant is
formed. Then it collapses into a supernova, this then forms into a neutron star.
Then a pulsar or black hole.…read more


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