Question
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?
Explanation
Statement 1 is correct: Being the fastest seismic waves, P waves always arrive at a seismograph before the slower S waves, which is exactly how seismologists distinguish them on a seismogram.
Statement 2 is correct: P waves are longitudinal, so particles oscillate back and forth in the same direction the wave travels — like a compression wave. S waves are transverse, moving particles perpendicular to the direction of propagation.
Both statements accurately describe seismic wave behaviour, so the answer is Option C.