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Which of the following statements is/are correct? 1. Secondary waves are compressional waves that are longitudinal in nature. 2. Primary waves are shear waves that are transverse in nature.

Which of the following statements is/are correct? 1. Secondary waves are compressional waves that are longitudinal in nature. 2. Primary waves are shear waves that are transverse in nature. Correct Answer Neither 1 nor 2

The correct answer is Neither 1 nor 2.

Key Points

Primary Waves:

  • Primary waves (P-waves) are compressional waves that are longitudinal in nature. Hence, Statement 1 is incorrect.
  • P waves are pressure waves that travel faster than other waves through the earth to arrive at a seismograph.
  • These waves can travel through any type of material, including fluids as well as solid.
  • They travel faster than S-waves.

Secondary Waves:

  • Secondary waves (S-waves) are shear waves that are transverse in nature. Hence, Statement 2 is incorrect.
  • S-waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses.
  • S-waves are slower than P-waves.

Important Points

  • Earthquake waves get recorded in seismographs located at far off locations.
  • It has been inferred indirectly using the time of travel of refracted and reflected seismic waves created by earthquakes.
  • The changes in seismic velocity between different layers cause refraction due to Snell's law.
  • S wave shadow zone forms the boundary of the outer core as it is in a liquid state.
  • There exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’.

                [ alt="shadow-2-SE" imaging earth interior physical geology first university of saskatchewan edition src="https://openpress.usask.ca/app/uploads/sites/29/2018/03/shadow-2-SE.png" style="height: 281px; width: 600px;">

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