A laser beam is directed onto two different aluminum plates
PHYSICS · Single correct · AP · Physics 2: Algebra-based · Geometric Optics · Geometric Optics
Problem
A laser beam is directed onto two different aluminum plates. Plate X has a highly polished surface, while Plate Y has a rough, brushed surface. The beam produces a sharp, bright spot on Plate X but a dim, widespread glow on Plate Y. Which of the following best explains this difference in appearance?
(a) The smoother surface of Plate X minimizes diffraction, so the reflected beam stays concentrated, whereas the rough surface of Plate Y diffracts the light, producing a widespread glow.
(b) On Plate Y the microscopic surface normals vary from point to point, so reflected rays leave in many directions.
(c) On Plate X the angle of incidence is smaller than it is on Plate Y, allowing a greater fraction of light to be reflected toward the viewer.
(d) Light striking Plate Y is partly absorbed because the law of reflection does not apply on rough surfaces.