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Seismic waves originate in the
Earths crust as a result of
movement between the tectonic
plates.
As tectonic plates move, potential
energy builds up between them,until there is too much energy to
be contained and it is released in
the form of a seismic wave.
The waves travel through the
ground, which is the medium. They
are also transferred into objects onthe ground. This is know as an
earthquake.
The strength of an earthquake is
measured using the Richter Scale.
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Primary waves (P waves) are the fastest and travelbetween 1,5 - 8 km/h, as they are longitudinal. Theycan pass through all three phases of matter and delivera large amount of energy to the surface in one go.
Secondary waves (S waves) are slower and can onlypass through a solid medium as they are transverse.They displace particles, so the energy is transferred tothe surface as rolling movement, which ischaracteristic of most earthquakes.
Surface waves (L waves) are the slowest and travel
along the Earths surface, transferring energy to trees,buildings, bridges etc. As a result they are the mostdestructive.
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Sound waves are partof the invisiblespectrum. They canonly be transmitted
through a medium suchas air or water. Sound waves also
cause particles tovibrate. They are
longitudinal waves andcan travel at differentspeeds and intensities.
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Sound waves have all the properties of otherwaves, but these can be translated slightlydifferently sue to the fact that sound is
produced.The amplitude of a sound wave equates to
the volume. Therefore, a greater amplitudemeans a louder volume.
The frequency of the sound wave equates tothe pitch (high or low). The greater thefrequency, the higher the pitch of the sound.
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Sound travels at different speedsaccording to environmental conditions.Temperature and moisture content can
affect how fast a sound travels.The speed of sound is 331.4 + 0.6Tc
m/s, where Tcis the temperature in Celcius.
When an object travels faster than thespeed of sound, it becomes supersonic oris said to break the sound barrier.
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Visible light is seen as white,but can be split using a prisminto its composite colours.These are red, orange, yellow,green. Blue indigo and violet.
Each colour light has a differentwavelength with violet havingthe shortest and red thelongest.
Light waves can travel througha vacuum. Light waves are thefastest known transverse wave
and travel at 299 792 458 m/s.Light is also able to exist aswaves and particles known asphotons which act differently.
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The human eye contains receiverscalled cones that see reflected lightin colour. This stimulates nerveswhich transmit electrical messagesto the brain, which interprets theimages as the correct colour.
As the human eye only seesreflected light, only the colour thatthe object reflects will be seen. A redapple is red because it reflects redlight and absorbs all the othercolours.
All primates have colour vision.However, sometimes there is a
problem with the cones and certaincolours cannot be seen. This iscalled colour-blindness and is agenetic disorder.
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Can you see the numbers in the
circles. If not, you may have
colour blindness.
There are three different types ofcones which distinguish red,
green and blue. If one or more
types are faulty, this leads to
being unable to distinguish
between colours. Very rarely, apersons cones do not work at all
and they only see in black and
white.