Paragraph:

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 $\sin i_{m}$.





Question:

For two structures namely $S_{1}$ with $n_{1}=\sqrt{45} / 4$ 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)