The following table gives the values of refractive indices of a few media:

$S.No.$	$1$	$2$	$3$	$4$	$5$
Medium	Water	Crown glass	Rock salt	Ruby	Diamond
Refractive index	$1.33$	$1.52$	$1.54$	$1.71$	$2.42$

Use this table to give an example of $(i)$ a medium pair so that light speeds up when it goes from one of these media to another. $(ii)$ a medium pair so that light slows down when it goes from one of these media to another.

(N/A) $(i)$ Light speeds up when it travels from an optically denser to an optically rarer medium. In other words, it travels from a medium of high refractive index to a medium of low refractive index. Therefore, one such pair is from crown glass $(1.52)$ into water $(1.33)$.
$(ii)$ Light slows down when it travels from an optically rarer to an optically denser medium. In other words, it travels from a medium of low refractive index to a medium of high refractive index. One such pair is from water $(1.33)$ into diamond $(2.42)$.