Final answer:
P-waves are longitudinal seismic waves that can propagate through liquids by refraction, resulting in a change in direction and a decrease in speed. This phenomenon, along with the absence of S-waves beyond certain angles, helped geologists discover that Earth has a liquid outer core.
Step-by-step explanation:
When P-waves, which are a type of seismic wave, travel through a liquid, their behavior changes due to the properties of the medium. Unlike S-waves (shear waves), which cannot travel through a liquid, P-waves are longitudinal waves and can propagate through both solid and liquid materials. However, as P-waves enter a liquid, such as Earth's liquid outer core, they experience refraction due to the change in density and bulk modulus of the fluid. This refraction causes the waves to bend and change direction. Additionally, the speed of P-waves decreases when they travel through a liquid compared to their speed in a more rigid material like rock.
Geologists have used the behavior of P-waves to learn more about the structure of the Earth's interior. The analysis of P-wave travel times and pathways, as well as the absence of S-waves beyond certain angles from the earthquake epicenter, have led to the understanding that Earth has a solid inner core surrounded by a liquid outer core. Both the speed of sound and its direction are affected by the liquid nature of the outer core, providing valuable information about the composition and temperature of Earth's interior.