waves 3 Flashcards
what does an ultra sound scanner use
an eletronic device called a transducer to produce ultra sound waves
how does an ultra sound scanner work
when a wave meets a boundary between two different materials, part of the wave is reflected
the wave travels back through the material to be detected by the transducer
the time taken to reach the transducer is used to calculate how far the boundary is
what can ultra sounds be used for
in medicine for scanning
why can ultra sounds be used for scanning
the waves are reflected at boundaries between different types of tissues
what is the focus of an earthquake
the point where an earthquake originates
what is the epicentre of an earthquake
closest point on earths surface to the focus
what does an earthquake produce
seismic waves
what are P-waves
longitudinal waves that produce the initial tremor and they refract at the boundary between the mantle and the core
what are s-waves
transverse waves that travel more slowly than p waves and produce tremors after a minute
where do s-waves not travel
through the liquid core of the earth
what do both p and s waves do as they travel through the mantle
bend because their speed gradually changes
what do L waves do
travel more slowly than P and S waves and only travel in earths crust
they arrive last and cause violent movement in crust
what is earthquake activity measured by
seisometers
what do seisometers do
help detect the epicentre
