Physics 1 Topic 4

Question	Answer
What are these waves called?	Seismic waves.
What are Seismometers?	Instruments that can detect these waves.
The place inside the Earth where rock suddenly moves or fractures is called the...	Focus of an earthquake.
What is the epicentre?	The point on the surface of the Earth directly above the focus.
What two types of waves do earthquakes cause?	P waves (longitudinal) and S waves (transverse).
What two types of waves do earthquakes cause?	P waves (longitudinal) and S waves (transverse).
What do P waves do?	They push and pull on the rock particles as the wave passes.
What do S waves do?	They move the rock particles from side to side as the wave passes.
What is the outermost layer of the Earth made out of?	Plates.
Tectonic plates are pushed by very slow moving...	Convection currents in the mantle.
What is frequency?	The number of complete waves that pass a point in one second.
What is it measured in?	Hertz (Hz)
What are sound waves?	Longitudinal vibrations that travel through a medium (A material).
What does the frequency of a sound wave determine?	The pitch of the sound.
Humans can hear sounds in the frequency range....	20 to 20,000 Hz (or 20kHz)
What are sounds with frequencies below 20Hz called?	Infrasound.
How are they detected?	Using microphones.
What is Infrasound useful for?	Studying animals.
Natural events such as volcanic eruptions create...	Infrasound waves and sounds we can hear.
What are sounds with frequencies higher than 20kHz called?	Ultrasound.
What is Sonar equipment used for? And where is it carried?	It is carried on ships or submarines to find the depth of the sea or to detect fish.
What happens when an ultrasound scan is made?	Some ultrasound waves are reflected each time the waves pass into a different medium.
What are earthquakes? And what do they cause?	Movements inside the Earth, that cause waves to be transmitted through the Earth.

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