Which statement describes P waves?
A). They start as surface waves.
B). They travel through liquids.
C). They vibrate from side to side.
D). They move slower than S waves.
The Correct Answer and Explanation is :
The correct answer is B) They travel through liquids.
Explanation:
P waves, also known as primary waves or pressure waves, are a type of seismic wave that is one of the two main types of body waves produced by an earthquake. They are the fastest seismic waves, and because of their speed, they are the first to be detected by seismographs after an earthquake. Understanding their characteristics can provide insights into how seismic waves travel through the Earth’s interior.
1. Travel through solids and liquids:
P waves are longitudinal waves, meaning that they cause the particles of the medium through which they pass to move back and forth in the direction of the wave propagation. This allows P waves to travel through both solids and liquids, unlike S waves (secondary waves), which can only travel through solids. When P waves travel through liquids (such as the Earth’s outer core), they slow down but continue to propagate. This ability to travel through both solids and liquids is a key characteristic that distinguishes them from S waves.
2. Speed and propagation:
P waves are the fastest type of seismic wave and are the first to be detected by seismographs. They move faster than S waves, which is why they are the first to arrive at a seismic station during an earthquake.
3. Nature of movement:
P waves do not vibrate side to side (which is the characteristic of S waves). Instead, the particles in the material move in the same direction as the wave, creating a compression and decompression effect along the path of propagation. This back-and-forth movement is what makes them longitudinal, compared to S waves, which are transverse waves and cause particles to move up and down or side to side.
4. Surface waves:
P waves are not surface waves, which are the slowest and most destructive waves. Surface waves, such as Love and Rayleigh waves, travel along the Earth’s surface rather than through its interior.
Thus, the correct answer to this question is B) They travel through liquids.