Tectonics,Sound & Light

7/27/2019 Tectonics,Sound & Light

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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.

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Tectonics,Sound & Light