Question

what is an optically rarer medium and an optically denser medium

Answer 1

Opticall rarer medium- in which lights speed is faster.
optically denser-speed of light is slower.

Answer 2

A medium ‘A’ is said to be optically denser then
medium ‘B’, if the speed of light in ‘A’ is lesser
than the speed of light in ‘B’ i.e the refractive
index of ‘A’ is greater than the refractive index of
‘B’.
A medium ‘A’ is said to be optically rarer then
the medium ‘B’, if the speed of light in ‘B’ is
greater than the speed of light in ‘A’ i.e the
refractive index of ‘A’ is lesser than the
refractive index of ‘B’.
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