Waves

• ultrasound is sound that vibrates at frequencies above 20,000 Hz
• when ultrasound passes through different mediums, some is reflected and some passes through and is refracted. this is called partial reflection
• ultrasound is used to scan foetuses by using an ultrasound device which can transmit and receive the ultrasound waves being fired at the foetus. every time it passes through a different medium some waves are reflected, and the timings and distributions are processed by a computer to form a live image.
• ultrasound can check the quality of products in industry by checking for early reflections that can indicate there is a crack
• ultrasound is used for sonar where boats fire ultrasound at the sea floor to find out how far away they are using distance=speedxtime, but the time is measured from being emitted, reaching the sea floor and also bouncing back
• earthquakes, volcanoes and explosions all create seismic waves which travel through the earth and can be detected by seismographs
• P waves are longitudinal, and can travel through solids and liquids
• s waves are transverse and can only travel through solids
• p waves are much faster than s waves
• s waves cannot pass through the liquid outer core
• scientists were able to discover the internal structure of the earth by measuring what types of waves could be measured in different parts of the world