Standing in front of a tall building, a girl whistles and hears its echo after 3.0s. The direction of her whistle makes an angle of 20∘ with the normal drawn to the face of the building at the point where the sound first strikes.
(i) Draw a labelled diagram showing the building, the girl, the incident sound ray, the reflected sound ray and all relevant angles.
(ii) Write the value of the angle of reflection in this case.
(iii) Taking the speed of sound in air as 340ms−1, calculate the distance between the girl and the building.