Correct Option
The correct option is (a) 1 only.
Explanation
Sound waves behave similarly to light waves; they can bounce off surfaces, a phenomenon known as reflection. When sound undergoes multiple reflections in a confined or complex space, it leads to phenomena such as echoes and reverberation. Managing these reflections is crucial in acoustics.
Statement-wise Analysis
- Statement 1 is Correct: The "rolling" or rumbling effect of thunder is caused by the successive reflections (or multiple echoes) of the sound produced by lightning. The sound waves bounce off various surfaces such as clouds, layers of air with different temperatures, and the land. These reflected waves reach the listener's ear at slightly different times, creating a prolonged, rolling sound rather than a single sharp crack.
- Statement 2 is Incorrect: Reverberation refers to the persistence of sound in a closed enclosure due to repeated reflections. To reduce reverberation and improve audio clarity, the roof and walls of an auditorium are covered with sound-absorbing materials (such as compressed fiberboard, rough plaster, or heavy curtains), not sound-reflecting materials. Sound-reflecting materials would increase the reverberation, making the sound indistinct.
Key Takeaway
Reverberation is the persistence of sound due to multiple reflections. To minimize it, surfaces must be covered with sound-absorbent materials, whereas the rolling of thunder is a natural example of multiple reflections.