- 04/28/2019 at 9:15 am #682984EduGorillaKeymasterSelect Question Language :
Directions: This paragraph is followed by a question which has four choices (1), (2), (3) and (4), out of which ONE or MORE THAN ONE are correct.
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 im are confined in the medium of refractive index n1. The numerical aperture (NA) of the structure is defined as sin im.
For two structures namely S1 with n1 = /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, which of the following options is/are correct?
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- NA of S1 immersed in water is the same as that of S2 immersed in a liquid of refractive index .
- NA of S1 immersed in liquid of refractive index is the same as that of S2 immersed in water.
- NA of S1 placed in air is the same as that of S2 immersed in liquid of refractive index .
- NA of S1 placed in air is the same as that of S2 placed in water.
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