Vibrations are periodic
waves of energy transmitted through matter.
Sound is a familiar and useful such energy and is used by both
bats and humans to locate objects that are shrouded in darkness.
> sound moves at varying speeds in various materials and also in
the same material at different temperatures
> sound waves demonstrate some of the same characteristics as light
such as reflection (echoes) and refraction (bending and lensing)
> man made seismic waves are used to locate structures deep in the
earth or below water.
The source of man made seismic waves can be air blasts or explosives.
> the huge seismic energies released by earthquakes are often used
to study the core of the earth
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