# Solar System, Generating Electricity, The Big Bang Everything on Physics

Solar System, Generating Electricity, The Big Bang Everything on Physics

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• Created by: waqaar
• Created on: 17-06-08 17:24

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Sound waves
Sound waves are longitudinal waves. Their vibrations occur in the same direction as
the direction of travel. Sound waves can only travel through a solid, liquid or gas.
Ultrasound
Ultrasound waves have frequencies above about 20kHz (20,000Hz). This is above
the normal hearing range for humans, so we cannot hear ultrasound.
Ultrasound waves can be use in medicine for prenatal scanning (checking unborn
babies). They can be used in industry for cleaning objects such as jewellery. They
can also be used in quality control procedures to check manufactured objects, such
as railway tracks and oil pipelines, for damage or defects.
Seismic waves (Higher Tier)
You should be able to explain how seismic waves can provide information about the
Earth's structure.
P waves and S waves
Earthquakes produce shockwaves called seismic waves. These waves can be
detected using seismographs. Some seismic waves are surface waves, while
others can travel through the Earth. The table summarises the properties of the two
types of seismic wave that can travel through the Earth.
P waves S waves
Type of wave longitudinal transverse
Relative speed faster slower
What can they travel through? solids and liquids solids only
The Earth's structure
The Earth is almost a sphere. These are its main layers, starting with the outermost:
The crust relatively thin and rocky
The mantle has the properties of a solid, but can flow very slowly
The outer core made from liquid nickel and iron
The inner core made from solid nickel and iron

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Evidence from seismic waves
The speed of P waves and S waves increases as they travel deeper into the
mantle. They travel through the Earth in curved paths, but they change direction
suddenly when they pass through the boundary between substances in different
states. The diagrams show what happens when P waves and S waves pass through
the Earth.
S waves cannot pass through the liquid outer core, but P waves can.…read more

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A summary
The table summarises the main types of electromagnetic radiation and a typical use
for each of them.
Gamma waves have a very high frequency. Gamma radiation cannot be seen or
felt. It mostly passes through skin and soft tissue, but some of it is absorbed by cells.
Gamma radiation is used to:
Sterilise surgical instruments.
Kill harmful bacteria in food.
Kill cancer cells (note that lower doses of gamma radiation could cause cells
to become cancerous).…read more

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Darker
skins absorb more ultraviolet light, so less ultraviolet radiation reaches the deeper
tissues. This is important because ultraviolet radiation can cause normal cells to
become cancerous.
Ultraviolet radiation is used in:
Sun beds
Security pens
Fluorescent lights (coatings inside the light absorb the ultraviolet light and
reemit it as visible light)
Infra red radiation is absorbed by the skin and we feel it as heat. It is used in
heaters, toasters and grills.…read more

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The speed of a comet increases as it gets closest to the sun, and is greatest when
the comet is nearest to the sun. Comets are often visible from Earth when they get
close to the sun, because the sun's heat vaporises material from the surface to form
a tail. As a comet moves away from the sun, its speed decreases. It is at its slowest
when it is furthest away from the sun.
The moon
A satellite is an object that orbits a planet.…read more

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The distances involved are huge: the distance from one star and another in a galaxy
is millions of times more than the distance between the planets in the solar system.
Meanwhile, the distance from one galaxy to another is millions of times more than
the distance between the stars in a galaxy. The universe contains at least one billion
galaxies.
SETI
Alien civilisations, which are capable of transmitting radio signals, may exist.…read more

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An optical fibre is a thin rod of highquality glass. Very little light is absorbed by the
glass. Light getting in at one end undergoes repeated total internal reflection, even
when the fibre is bent, and emerges at the other end.
Information such as computer data and telephone calls can be converted into
electrical signals. These can be carried through cables, or transmitted as

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Analogue signals
Noise adds extra random information to analogue signals. Each time the signal is
amplified the noise is also amplified. Gradually, the signal becomes less and less
like the original signal. Eventually, it may be impossible to make out the music in a
radio broadcast against the background noise, for example.
Digital signals
Noise also adds extra random information to digital signals. However, this noise is
usually lower in amplitude than the ON states.…read more