A narrow beam of sound from a loud-speaker strikes a smooth concrete wall in an open playground. The incident ray makes an angle of 35∘ with the normal to the wall.
(i) State the law of reflection for sound.
(ii) Using a simple ray picture and the behaviour of air particles at a rigid boundary, explain why the incident and reflected rays make equal angles with the normal.
(iii) Give two practical situations inside an auditorium where this property of reflection of sound is deliberately used to improve audibility.