CONCEPT: Reverberation: - This persistence of sound in a closed enclosure, due to continuous reflections at the walls or the floor or the ceiling of the enclosure, even after the source has stopped producing sound is known as 'reverberation'. - If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo. EXPLANATION: - From the above, it is clear that the persistence of sound in a closed enclosure, due to continuous reflections at the walls or the floor or the ceiling of the enclosure, even after the source has stopped producing sound is known as 'reverberation'. Therefore option 1 is correct. - Dispersion of light is the phenomenon of splitting of a beam of white light into its constituent colours on passing through a prism. - The bending of the ray of light passing from one medium to the other medium is called refraction. - Diffraction is defined as the bending of waves around the corners of an obstacle. Important Point - To reduce reverberation, the roof and walls of the auditorium are generally covered with sound-absorbent materials like compressed fibreboard, rough plaster, or draperies. - The seat materials are also selected based on their sound-absorbing properties.