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: C. Both statements about seismic waves are correct. Statement 1 is CORRECT. P-waves (Primary or pressure waves) are the FASTEST body waves; they arrive at the seismograph FIRST. S-waves (Secondary or shear waves) are slower and arrive after. This time-lag between P and S arrivals is used to determine the distance to the earthquake epicentre via the time-travel method. Statement 2 is CORRECT. P-waves are LONGITUDINAL waves: particle motion is PARALLEL (to and fro) to the direction of wave propagation. They cause compression and rarefaction of the medium. P-waves travel through solids, liquids and gases. S-waves are TRANSVERSE waves: particle motion is PERPENDICULAR (up and down or side to side) to the direction of propagation. S-waves travel only through SOLIDS — they cannot pass through liquid outer core, which produces the S-wave shadow zone evidence for Earth's interior structure. Source: NCERT Class 11 Fundamentals of Physical Geography Ch 3 (Interior of the Earth).