Light guidance in an optical fiber can be understood by considering a structure comprising of thin solid glass cylinder of refractive index n₁ surrounded by a medium of lower refractive index n₂. The light guidance in the structure takes place due to successive total internal reflections at the interface of the media n₁ and n₂ as shown in the figure. All rays with the angle of incidence i less than a particular value of iₘ are confined in the medium of refractive index n₁. The numerical aperture (NA) of the structure is defined as sin iₘ.
Physics · Geometrical optics · law of refraction and total internal reflection
Light guidance in an optical fiber can be understood by considering a structure comprising of thin solid glass cylinder of refractive index n₁ surrounded by a medium of lower refractive index n₂. The light guidance in the structure takes place due to successive total internal reflections at the interface of the media n₁ and n₂ as shown in the figure. All rays with the angle of incidence i less than a particular value of iₘ are confined in the medium of refractive index n₁. The numerical aperture (NA) of the structure is defined as sin iₘ.
Sub-question 1
For two structures namely S₁ with n₁ = √45/4 and n₂ = 3/2, and S₂ with n₁ = 8/5 and n₂ = 7/5 and taking the refractive index of water to be 4/3 and that of air to be 1, the correct option(s) is (are)
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Sub-question 2
If two structures of same cross-sectional area, but different numerical apertures NA₁ and NA₂ (NA₂ < NA₁) are joined longitudinally, the numerical aperture of the combined structure is
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