February 4, 2026

Consider the following statements

Q. Consider the following statements with reference to Secondary waves (S-Waves) generated during an earthquake :

UPSC CDS Examination (I) 2025 – General Knowledge

1. They create troughs and crests in the material through which they pass.
2. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation:

Secondary waves (S-waves) are a type of body wave generated during an earthquake. They are also known as shear waves.

🔹 Statement 1: Correct
S-waves are transverse waves, meaning the particles of the medium move at right angles to the direction of wave propagation. This transverse motion produces crests and troughs in the material through which the wave passes.

🔹 Statement 2: Correct
In S-waves, the direction of vibration is perpendicular to the direction of wave travel. This vibration generally occurs in the vertical plane (though it can also be horizontal), which is a defining characteristic of shear waves.

Answer: (c) Both 1 and 2

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