During a thunderstorm, the sound is heard over a long time. this phenomenon is referred to as?

1. Analyze the question The question asks why thunder seems to last a long time (rumbling) instead of being a single short bang.

2. Explain the concept

• Diffraction: bending of waves around obstacles or through gaps.
• Refraction: change in direction of waves as they pass through media of different density or temperature, so their speed changes.
• Superposition: combining of two or more waves at the same point.
• Reverberation: the persistence of sound caused by repeated reflections (echoes) from surfaces such as clouds, hills and buildings. The reflected sounds reach the ear one after another, so the sound seems prolonged.

3. Step-by-step solution

• Lightning heats the air suddenly along its whole path, which can be several kilometres long. Sound is produced at every point along it.
• Sound from the nearer parts of the path reaches you first and sound from the farther parts arrives later, because sound travels at a finite speed (about 340 m/s).
• Clouds, the ground and hills reflect the sound many times. These reflections reach you at slightly different times.
• The result is a long, rolling rumble. The prolonging of sound by multiple reflections is called reverberation.

4. Answer Option D (reverberation). Note that "reveraberation" in the option is simply a misspelling of "reverberation".

5. Exam tip

• Echo is a single, distinct reflection, heard separately from the original sound.
• Reverberation is many reflections merging, so the sound seems to last longer.
• Remember: thunder rumble = reverberation.