Correct Option
The correct option is (a).
Explanation
Sound waves are mechanical waves that propagate through a medium via the oscillation of particles. A slinky (a coiled spring) is a standard physical model used to demonstrate wave mechanics. It can illustrate both transverse waves (by moving the end side-to-side) and longitudinal waves (by moving the end back-and-forth), the latter being the mode of propagation for sound in fluids.
Statement-wise Analysis
- Statement 1 is Correct: A slinky can demonstrate longitudinal waves. When the coils are pushed and pulled along the length of the spring, the disturbance moves parallel to the direction of the coils' oscillation. This mirrors the propagation of sound waves in air.
- Statement 2 is Incorrect: In a longitudinal wave, the regions where the particles of the medium (or coils of the slinky) are crowded close together are regions of high density and pressure. These are technically termed compressions, not rarefactions.
- Statement 3 is Incorrect: The regions where the particles of the medium (or coils of the slinky) are spread further apart are regions of low density and pressure. These are technically termed rarefactions, not compressions.
Key Takeaway: Sound propagates as a longitudinal wave characterized by alternating regions of high pressure called compressions and low pressure called rarefactions.