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Q65 (IAS/2023) Geography › World Physical Geography › Seismology and volcanism Official Key

Consider the following statements : 1. In a seismograph, P waves are recorded earlier than S waves. 2. 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?

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is Option 3 (Both 1 and 2) because both statements accurately describe the physical properties of seismic waves.

  • Statement 1 is correct: P-waves (Primary waves) are longitudinal waves that travel faster than S-waves (Secondary waves). Due to their higher velocity, P-waves are the first to be detected and recorded by a seismograph after an earthquake occurs, followed by the slower S-waves.
  • Statement 2 is correct: This describes the particle motion of each wave type. P-waves are compressional; particles vibrate parallel (to and fro) to the direction of energy propagation. In contrast, S-waves are transverse; particles move perpendicular (up and down or side to side) to the wave's path.

Since P-waves always precede S-waves and their respective vibration patterns are correctly identified, both statements are scientifically sound, making Option 3 the right choice.

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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements : 1. In a seismograph, P waves are recorded earlier than S waves. 2. In P waves, the individual parti…
At a glance
Origin: From standard books Fairness: High fairness Books / CA: 10/10 · 0/10
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This is a classic 'bread and butter' question directly from NCERT Class XI (Fundamentals of Physical Geography). It is a high-fairness static question. If you get this wrong, you are at a severe disadvantage because the 'serious crowd' will mark this with 100% accuracy. No current affairs linkage required.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
In a seismograph recording, are P waves recorded earlier than S waves?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Primary Waves (P-Waves) > p. 60
Presence: 5/5
“• Primary waves are called so because they are the fastest among the seismic waves and hence are recorded first on the seismograph.• P-waves are also called as the • longitudinal waves because the displacement of the medium is in the same direction as, or the opposite direction to, (parallel to) the direction of propagation of the wave; or• compressional waves because they produce compression and rarefaction when travelling through a medium; or• pressure waves because they produce a change in pressure in the medium.• P-waves create density differences in the material leading to stretching (rarefaction) and squeezing (compression) of the material.• P-waves are of relatively high frequency and are the least destructive among the earthquake waves.”
Why this source?
  • Explicitly states P-waves are the fastest seismic waves and therefore are recorded first on the seismograph.
  • Describes P-waves as longitudinal/compressional waves whose transmission properties explain their rapid arrival.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Secondary Waves (S-Waves) > p. 62
Presence: 5/5
“• Secondary waves (secondary they are recorded second on the seismograph) or S-waves are also called transverse waves or shear waves or distortional waves. They are analogous to water ripples or light waves. They arrive at the surface after the P-waves.• Transverse waves or shear waves mean that the direction of vibrations of the particles in the medium is perpendicular to the direction of propagation of the wave. Hence, they create troughs and crests in the material through which they pass (they distort the medium).• These waves are of high frequency and possess slightly higher destructive power compared to Pwaves.”
Why this source?
  • Labels S-waves as 'secondary' and notes they are recorded second on the seismograph.
  • Explicitly states S-waves arrive at the surface after the P-waves and are transverse (shear) in nature.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Why Do P-Waves Travel Faster Than S-Waves? > p. 61
Presence: 4/5
“• P-waves are about 1.7 times faster than the S-waves. P-waves are compression waves that apply a force in the direction of propagation and hence transmit their energy quite easily through the medium and thus travel quickly. On the other hand, S-waves are transverse waves or shear waves (the motion of the medium is perpendicular to the direction of propagation of the wave) and are hence less easily transmitted through the medium.”
Why this source?
  • Provides a quantitative speed relation: P-waves are about 1.7 times faster than S-waves.
  • Explains the physical reason (compression waves transmit energy more quickly than shear waves), supporting earlier arrival of P-waves.
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Statement analysis

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SIMILAR QUESTIONS

CDS-II · 2024 · Q95 Relevance score: 2.62

Which one of the following statements regarding S-waves is not correct?

NDA-II · 2025 · Q115 Relevance score: 1.74

Which of the following statements with reference to shadow zones in an event of an earthquake is/are correct ? 1. Zone between 105° and 145° from epicentre was identified as the shadow zone for both P-waves and S-waves 2. The shadow zone of P-waves is much larger than that of the S-waves Select the answer using the code given below :

CDS-I · 2025 · Q1 Relevance score: 1.50

Consider the following statements with reference to Secondary waves (S-Waves) generated during an earthquake : 1. They create troughs and crests in the material through which they pass. 2. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Which of the statements given above is/are correct ?

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Consider the following statements 1. Light waves can travel in vacuum. 2. Light waves can be refracted. 3. Light waves are electromagnetic. Which of the statements given above are correct ?

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Consider the following statements: 1. A flute of smaller length produces waves of lower frequency. 2. Sound travels in rocks in the form of longitudinal elastic waves only. Which of the statements given above is/are correct?