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?

Q 1 / 6

UPSC CSE Prelims 2023

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?

Correct Option (c):

Both statements are correct.

Statement 1: P waves (Primary waves) are the fastest seismic waves. They are compressional waves that can travel through solids, liquids, and gases. S waves (Secondary waves) are slower shear waves that can only travel through solids. Due to their higher velocity, P waves arrive and are recorded earlier than S waves on a seismograph.
Statement 2: P waves are longitudinal waves, meaning the particles of the medium vibrate parallel to the direction of wave propagation (to and fro motion). S waves are transverse waves, meaning the particles of the medium vibrate perpendicular (at right angles) to the direction of wave propagation (up and down or side to side motion).

Incorrect Options:

Option (a) 1 only: This is incorrect because Statement 2 is also factually correct regarding the nature of P and S waves.
Option (b) 2 only: This is incorrect because Statement 1 is also factually correct regarding the arrival times of P and S waves.
Option (d) Neither 1 nor 2: This is incorrect because both statements accurately describe the characteristics of P and S seismic waves.

SOURCENCERT Class 11 Geography Chapter 3: Interior of the Earth