A sheet of glossy card stock reflects incident light such that of the incident power…
PHYSICS · Multi-part · CBSE · Physics · Light — Reflection and Refraction · Light — Reflection and Refraction
Problem
A sheet of glossy card stock reflects incident light such that 30% of the incident power is concentrated into a narrow specular lobe centered on the angle predicted by the law of reflection, while the remaining 70% is uniformly scattered over the forward half-space.
A 50mW red laser beam strikes the sheet at an angle of incidence of 25∘ with respect to the normal.
A circular screen of area 25cm2 is placed 75cm from the point of incidence so that its center lies exactly on the specular ray.
Respond to the following prompts.
(a) Calculate the optical power that strikes the screen due to the specular component.
(b) Assuming the diffuse component is emitted uniformly into 2π steradians, determine the optical power from the diffuse component that strikes the screen. (Treat the illuminated spot on the sheet as a point source.)
(c) Compare the brightness contributions from the specular and diffuse components on the screen. State which component dominates and support your answer with quantitative reasoning.