# Edexcel Physics 1 Topic 4

 What name is given to sound with a frequency greater than 20 000 Hz? Ultrasound Name three uses of ultrasound Sonar - detecting objects under watercommunication between animalsscanning unborn babies What name is given to sound with a frequency less than 20 Hz? Infrasound Name three uses of infrasound communication between animalsdetecting animal movement in remote locationsdetecting volcanic eruptions and meteors What do we call waves that travel through the ground? Seismic Name two things that can cause seismic waves explosionsearthquakes Are seismic waves longitudinal or transverse? They can be either. Longitudinal waves are also known as P waves. Transverse waves are also known as S-waves Which boundaries within the Earth reflect or refract seismic waves? between the crust and mantlebetween the mantle and the core What do we call the moving plates in the Earths crust? Tectonic plates What causes tectonic plates to move? Convection currents in the Earths mantle What is the cause of Earthquakes? Tectonic plates sliding past each other and getting caught. When sufficient pressure builds up, they are released causing an earthquake. What do we call the number of complete waves that pass a point in a second? The wave frequency Name three uses of sonar (using ultrasound) mapping the sea floordetecting submarinesdetecting shoals of fish What is the epicentre of an Earthquake? The point on the Earths surface directly above the focus of the earthquake What are seismometers used for? To measure the amount that the ground shakes What is a tsunami? A huge wave in the sea caused by an earthquake under the sea What is the unit of frequency? Hertz (Hz) Which waves travel the fastest, P or S? P (seismic longitudinal) waves travel faster than S waves AuthorHLHSscience ID199158 Card SetEdexcel Physics 1 Topic 4 DescriptionEdexcel Physics 1 Topic 4 Updated2014-03-23T10:10:36Z Show Answers