Prelims 2023 · Geography · Question 75
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?
Answer
Both 1 and 2
1. Correct. P (Primary) waves travel faster than S (Secondary) waves, so they reach a seismograph first and are recorded earlier.
2. Correct. In P waves, particles vibrate parallel to the direction of propagation (to and fro), while in S waves, particles vibrate perpendicular to the direction of propagation (up and down/sideways).
Hence, both 1 and 2 are correct.