Why cant P or S waves be detected in the shadow zone?

P (primary) waves can travel through both liquids and solids, while S (secondary) waves can only travel through solids. The shadow zone for seismic waves occurs on the opposite side of the Earth from an earthquake's epicenter, where S waves are not detected because they cannot pass through the liquid outer core. P waves are detected in the shadow zone but at a reduced intensity due to their refraction when transitioning from the solid mantle to the liquid outer core. Thus, the absence of S waves and the diminished presence of P waves in this region explain why it is termed a shadow zone.