Consider the following statements:In a seismograph, P waves are recorded earlier than S waves.In P w

Q: What is UPSC Prelims?

UPSC Prelims is a competitive examination conducted in India. This question is from the 2023 UPSC Prelims Geography paper.

Q: How can I prepare for UPSC Prelims Geography?

To prepare for UPSC Prelims Geography, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2023 question covers Interior of the Earth – Layers, Plate Tectonics & Earthquakes topic.

Q: What is the difficulty level of this question?

This UPSC Prelims 2023 Geography question has a easy difficulty level and is marked as an important question.

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Question

Consider the following statements:In a seismograph, P waves are recorded earlier than S waves.In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation.Which of the statements given above is/are correct?

Accepted Answer

Correct Answer: C — Both statements are correctStep-by-step Solution:Statement 1: Correct – P‑waves (primary waves) are faster than S‑waves (secondary waves). Thus, on a seismograph, P‑waves arrive first, followed by S‑waves.Statement 2: Correct – P‑waves are compressional (longitudinal): particle motion is parallel to wave propagation. S‑waves are shear (transverse): particle motion is perpendicular (up‑down or side‑to‑side) to the direction of travel.Why other options are incorrect:Option A (1 only): Statement 2 is also correct.Option B (2 only): Statement 1 is also correct.Option D (Neither): Both are correct.Key Concept: Seismic waves: P‑waves travel through solids, liquids, and gases; S‑waves only through solids. The time difference (S‑P interval) is used to locate earthquake epicentres. Surface waves (Love and Rayleigh) cause most damage.

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More Questions from Interior of the Earth – Layers, Plate Tectonics & Earthquakes

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