SOLAR SYSTEM

Detailed explanation-1: -Both P and S waves travel outward from an earthquake focus inside the earth. The waves are often seen as separate arrivals recorded on seismographs at large distances from the earthquake. The direct P wave arrives first because its path is through the higher speed, dense rocks deeper in the earth.

Detailed explanation-2: -Refraction is the change in direction of a wave at such a boundary.

Detailed explanation-3: -Seismic refraction uses elastic waves refracted at earth layers and travelling long distances along the earth while seismic reflection utilises reflections that bounce back near-vertically from layer interfaces.

Detailed explanation-4: -Refraction of seismic waves causes them to curve away from a direct path. Reflection causes them to glance off certain surfaces (e.g. core mantle boundary) when they hit it at too shallow of an angle.