Assertion (A): The ceilings of cinema halls and concert halls are generally…

Concept: Sound obeys the laws of reflection: the angle of incidence equals the angle of reflection at every point on a surface. A flat surface has one consistent surface-normal direction, so it reflects an incoming wavefront back in a single, concentrated direction. A curved (concave) surface has a normal that changes continuously from point to point, so it reflects the very same incoming sound outward across many different directions instead of concentrating it.

Application: Cinema and concert hall ceilings are deliberately built with a curved shape for exactly this reason. Sound produced on the stage or by the speakers strikes the curved ceiling and is reflected outward across a spread of directions, so it reaches the back rows, side sections, and corners of the hall with fairly even intensity, instead of bouncing back and forth strongly in only one narrow zone. This matches Assertion (A), that such ceilings are curved, and is directly explained by Reason (R), that a curved surface reflects sound in all directions.

Cross-check: Compare this with a flat ceiling: sound would reflect off it at one fixed angle, concentrating the reflected sound in specific limited zones and leaving other areas comparatively sound-deficient, along with pockets of noticeable echo. That contrast is exactly why auditoriums use curved ceilings rather than flat ones, confirming that (R) is not just true but is the correct causal explanation for (A).

Hence, both (A) and (R) are true, and (R) correctly explains (A).