exploring structures using waves

• studying the properties and paths of waves through structures can give you clues to some of the properties of the structure that cant see by the eye . you can do this by using different waves like ultrasound and seismic waves
• earthquake causes seismic waves which travel out through the earth, we detect these waves all over the surface of the planet using seismometers
• seismologists work out the time it takes for the shock waves to reach each seismometer they also note which parts of earth don't receive the shock waves at all
• when seismic waves reach a boundary between different layers of material inside the earth, some waves are absorbed and some refracted
• most of the time if the wave is refracted they change speed gradually, resulting in a curved path but when the properties change suddenly the wave speed changes abruptly
• there are two different types of seismic waves - P waves and S waves
• seismic waves have allowed us to understand the size of the Earths core and internal structure
• P waves are longitudinal. travel through solids and liquids, travel faster than S waves
• S waves are transverse and cant travel through liquids or gases, slower