$($e$)$ Given that for a graded index fibre with numerical aperture $($NA$)$ of $0\mathrm{.}275$ operating at

$1330$ nm$,$ calculate the Rayleigh scattering loss in dB$/$km $(2\mathrm{.}5$ marks$)$

$($f$)$ Now, given that we have a step index fibre with numerical aperture $($NA$)$ of $0\mathrm{.}275$

operating at $1330$ nm$,$ calculate the Rayleigh scattering loss in dB$/$km $(2\mathrm{.}5$ marks$)$