While aligning a solar telescope at sunset, an astronomer sees sunlight reflected from a distant glass façade but cannot directly view the incoming sunlight itself. To point the telescope at the Sun, the astronomer mentally traces the observed reflected ray backward through space.
(a) Describe the physical principle that allows the astronomer to infer the incoming direction of the sunlight by reversing the observed path of the reflected ray.
(b) Outline, in complete sentences, the sequence of reasoning the astronomer should follow to locate the Sun’s position in the sky using only the orientation of the façade and the direction of the reflected ray.
(c) Explain why this reasoning remains valid even if the façade is rotated to a different orientation, provided its surface remains flat and smooth.