Consider the following statements concerning earthquake waves: 1. Bod...
The correct answer is option 'C' - 1 and 2 only. Let's understand each statement.
1. Body waves are generated due to the release of energy at the focus and move in all directions travelling through the body of the Earth.
- Body waves are seismic waves that travel through the interior of the Earth. They are generated due to the release of energy at the focus of an earthquake. There are two types of body waves: P waves (primary waves) and S waves (secondary waves).
- P waves are the fastest seismic waves and they travel through solids, liquids, and gases. They move in a push-pull or compressional motion, causing particles in the material to move back and forth in the direction of wave propagation. P waves can travel through both the Earth's mantle and core.
- S waves are slower than P waves and can only travel through solids. They move in a shearing or shaking motion, causing particles in the material to move perpendicular to the direction of wave propagation. S waves cannot travel through the Earth's outer core, which is liquid.
- Therefore, the first statement is correct as body waves are generated at the focus of an earthquake and they travel in all directions through the body of the Earth.
2. The body waves interact with the surface rocks and generate a new set of waves called surface waves.
- Surface waves are seismic waves that travel along the Earth's surface. They are generated when body waves interact with the surface rocks. Surface waves are slower than body waves but they cause more damage during an earthquake due to their larger amplitudes.
- There are two types of surface waves: Love waves and Rayleigh waves. Love waves move in a side-to-side motion, similar to the motion of a snake or a wave on the surface of water. Rayleigh waves move in an elliptical motion, causing particles in the material to move in a rolling motion.
- Therefore, the second statement is correct as body waves interact with surface rocks and generate surface waves.
3. The denser the material, the lower is the velocity of these waves.
- This statement is incorrect. The velocity of seismic waves depends on the properties of the material through which they travel, including its density, elasticity, and rigidity. In general, denser materials tend to have higher velocities for seismic waves.
- For example, P waves travel faster through solids compared to liquids and gases because solids are denser and have higher elasticity and rigidity. Similarly, S waves can only travel through solids because they require a certain level of density and rigidity to propagate.
- Therefore, the third statement is incorrect as the velocity of seismic waves is generally higher in denser materials.
In conclusion, only statements 1 and 2 are correct.
Consider the following statements concerning earthquake waves: 1. Bod...
- The two types of earthquakes are body waves and surface waves. Waves that are generated from the release of energy at the focus travel through the body by moving in all directions. Hence, it is named body waves.
- Interaction between body waves and the rock’s surface generates a new set of waves. This is called surface waves. These waves move along the surface. Because these waves travel through materials that have different densities, the velocity changes.
- The density of the material is directly proportional to the velocity, that is, if the material is denser, the velocity is higher. There is a change in direction of the waves when they get reflected or refracted by materials with different densities.