The shadow zone for 'P' seismic waves is extended at what angular distance from the focus of earthquake?

Question

Accepted Answer

The shadow zone for P-waves extends from 103° to 143° on *both* sides of the earthquake's focus. This is why Option 3 is the correct answer.

Here's a detailed explanation:

*   **Why Option 3 is Correct:** P-waves are refracted (bent) as they travel through the Earth's mantle and core. When P-waves encounter the core-mantle boundary, their path bends significantly due to the change in density and composition. This bending creates a zone where direct P-waves are not received. This shadow zone begins at approximately 103° from the earthquake's epicenter. However, some P-waves are able to diffract around the core, but they are significantly weakened and arrive later than expected. The shadow zone ends at approximately 143° from the epicenter. Because this refraction occurs on all sides of the Earth relative to the earthquake's focus, the shadow zone exists on *both* sides, extending from 103° to 143°.

*   **Why Option 1 is Incorrect:** Option 1 states "103° to 103°". This implies a single point, not a zone. The P-wave shadow zone is a range of angular distances, not a single degree.

*   **Why Option 2 is Incorrect:** Option 2 states "143° to 143°". Similar to Option 1, this implies a single point, not a zone. While 143° is the *end* of the P-wave shadow zone, the zone itself starts at 103°.

*   **Why Option 4 is Incorrect:** Option 4 states "165° to 165°". This is incorrect because the P-wave shadow zone does not extend to 165°. The shadow zone ends at 143°.