The correct option is 2 and 3 only.
Explanation
Earthquake waves are classified into Body Waves and Surface Waves. Body waves are generated due to the release of energy at the focus and move in all directions traveling through the body of the Earth. They are further divided into P-waves (Primary waves) and S-waves (Secondary waves).
Statement-wise Analysis
- Statement 1 is Incorrect: P-waves are longitudinal waves that vibrate parallel to the direction of the wave. A distinct characteristic of P-waves is that they can travel through gaseous, liquid, and solid materials. They are not restricted to solids only.
- Statement 2 is Correct: S-waves are transverse waves that vibrate perpendicular to the direction of wave propagation. A crucial property of S-waves is that they can travel only through solid materials. This characteristic helped seismologists deduce that the Earth's outer core is in a liquid state, as S-waves cannot pass through it.
- Statement 3 is Correct: The velocity of seismic waves is directly related to the properties of the material through which they travel. As waves move through layers with different densities and elasticities, their velocity changes. Generally, velocity increases as the waves travel through denser materials deep inside the Earth. This change in velocity causes the waves to refract (bend).
Key Takeaway
P-waves can travel through all states of matter (solid, liquid, gas), whereas S-waves can travel only through solids. The variation in material density within the Earth causes seismic waves to change velocity and refract.