⚛️ Physics · Ray Optics and Optical Instruments · NEET & JEE

An optical fibre has a core of refractive index 1.60 and cladding of refractive index 1.50. The critical angle at the core-cladding interface is about:

Answer: 69.6°.

A 41.8°
B 48.6°
C 61.0°
D 69.6°

Correct answer: D. 69.6°

Explanation: sinθ_c = n_clad/n_core = 1.50/1.60 = 0.9375, so θ_c = 69.6°.

Concave mirror ray diagram with an object drawn as a candle on the principal axis, the focal point F marked, and the parallel ray and focal ray reflecting to form an inverted real image

Concave mirror ray construction: a ray parallel to the axis reflects through F, and a ray through F reflects parallel, locating the inverted real image. Image: Maxmath12, CC0, via Wikimedia Commons.

Concept context

Reflection, refraction, lenses, mirrors, total internal reflection.

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An optical fibre has a core of refractive index 1.60 and cladding of refractive index 1.50. The critical angle at the core-cladding interface is about:

Concept context

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