, NA of S 1 immersed in water is the same as that of S 2 immersed in a liquid of refractive index

, NA of S 1 immersed in liquid of refractive index is the same as that of S 2 immersed in water NA 1 + NA 2

and NA of S 1 placed in air is the same as that of S 2 immersed in liquid of refractive index NA 1

. ONE OR MORE THAN ONE of these four option(s) is(are) correct For each question, darken the bubble(s) corresponding to all the correct option(s) in the ORS Marking scheme: +4 If only the bubble(s) corresponding to all the correct option(s) is(are) darkened 0 If none of the bubbles is darkened – 2 In all other cases PARAGRAPH 1 Light guidance in an optical fiber can be understood by considering a structure comprising of thin solid glass cylinder of refractive index n 1 surrounded by a medium of lower refractive index n 2 . The light guidance in the structure takes place due to successive total internal reflections at the interface of the media n 1 and n 2 as shown in the figure. All rays with the angle of incidence i less than a particular value i m are confined in the medium of refractive index n 1 . The numerical aperture (NA) of the structure is defined as sin i m . (i) For two structures namely S 1 with and n 2 = 3/2, and S 2 with n 1 = 8/5 and n 2 = 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) NA of S 1 placed in air is the same as that of S 2 placed in water (ii) If two structures of same cross-sectional area, but different numerical apertures NA 1 and NA 2 (NA 2 < NA 1 ) are joined longitudinally, the numerical aperture of the combined structure is NA 2