The diagram below is a cross-section through the Earth. The black and white rays represent the paths of P-waves and S-waves respectively as they travel through the Earth from an earthquake epicenter. Examine the diagram, then answer the question that follows.

Question

Which of the following statements best explains the P-wave shadow zone?
A.
Unlike S-waves, P-waves are not capable of moving in a curved path, and thus travel through the liquid outer core.
B.
P-waves are attracted to the electrical currents in the liquid outer core, and thus are pulled towards the core and away from the mantle.
C.
As P-waves move from the mantle into the liquid outer core, they refract due to the change in density.
D.
P-waves carry more energy than S-waves, thus enabling them to travel through Earth in nearly straight paths.

Answer 1

The statement that best explains the P-wave shadow zone is:

C. As P-waves move from the mantle into the liquid outer core, they refract due to the change in density.

This is correct because P-waves (primary waves) are compressional waves that can travel through both solid and liquid materials. However, when they encounter a boundary between different materials, such as the transition from the solid mantle to the liquid outer core, they can change direction (refract) due to the difference in physical properties (density). This refraction causes the P-wave shadow zone, where no P-waves are detected beyond a certain angle from the epicenter of the earthquake.