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?
Show answer
Answer: C. Statement 1 is correct: P waves are fastest, so they reach the seismograph first. Statement 2 is correct: in P waves particles move back and forth along the direction of travel, while in S waves they move at right angles to it. So both.
Watch for: Students sometimes doubt the 'up and down' wording, but it correctly means perpendicular motion.
Why the other options are wrong
- A. Wrong because statement 2 is also correct.
- B. Wrong because statement 1 is also correct.
- D. Wrong because both statements are correct.
Source to check: NCERT Class 11 Fundamentals of Physical Geography, Ch 3 Interior of the Earth (earthquake waves)
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.