A student places three different objects under an overhead lamp so that each receives the same illumination: (1) a page of newsprint covered with black text, (2) the glossy cover of a magazine, and (3) a small household mirror. The student attempts to read the printed words in the reflection from each object while looking from a variety of viewing angles.
(a) Describe qualitatively what the student sees for each object when trying to read the text in reflection.
(b) Give a detailed explanation for the differences you described in part (a) using the concepts of surface normals and the two fundamental reflection types.
(c) The mirror clearly reproduces images yet makes the text unreadable, whereas the newsprint allows the text itself to be read but does not form sharp images of surrounding objects. Explain how the roughness scale of each surface relative to visible wavelengths accounts for this observation.
(d) The student now replaces the overhead lamp with a point-like red LED positioned close to the line of sight. Predict how the brightness and readability of the newsprint’s reflection will change, if at all, and justify your prediction.