Question

For a light pipe as shown in the figure:

(A) Optical density of core should be greater than the optical density of cladding.
(B) r and θ will always be equal.
(C) Optical density of cladding is $\frac{sinθ sin i}{sin r}$.
(D) Optical density of cladding is $\frac{sin r sin i }{sin θ}.$
Choose the correct answer from the options given below:

• A. (A), (B), and (D) only
• B. (A), (B), and (C) only
• C. (A) only
• D. (B), (C), and (D) only

Answer 1

Answer: (C)

(A) only

Answer 2

In a light pipe, total internal reflection occurs when the refractive index (or optical density) of the core is greater than that of the cladding. This allows the light to be confined within the core. The angles r and θ depend on Snell’s law, and they are not always equal. Therefore, only statement (A) is correct.