A laser pointer is pointed from air toward three separate transparent plates—Plate X,…
PHYSICS · Multi-part · CBSE · Physics · Light — Reflection and Refraction · Light — Reflection and Refraction
Problem
A laser pointer is pointed from air toward three separate transparent plates—Plate X, Plate Y, and Plate Z—each made of a different unknown material. In each trial, the incident beam strikes the plate at the same angle of incidence measured from the normal. When viewed from above, you observe the following qualitative outcomes:
• In Plate X the refracted beam bends noticeably toward the normal.
• In Plate Y the refracted beam is visible but appears to continue almost undeviated.
• In Plate Z the refracted beam bends markedly away from the normal.
Assume all plates are thicker than the beam path so that only the first interface matters.
Answer the following questions. Provide clear reasoning based only on the relative magnitudes of the indices of refraction and the idea of angles measured from the normal.
(a) Rank the indices of refraction of Plates X, Y, and Z from largest to smallest. Justify your ranking qualitatively.
(b) Rank the magnitudes of the deviations (angle between incident and refracted rays) produced by the three plates from greatest to least. Explain why your ranking follows from part (a).
(c) Suppose a beam enters Plate Y along the normal. Predict the path the light will follow inside the plate and at its exit surface back into air. Explain your prediction.