Answer
Speed of light in condensate is $v=19.108m/s$
Work Step by Step
refractive index is defined as
$n=\frac{c}{v}$
$c$=speed of light in vacuum
$v$= speed of light in material
we can rewrite above equation as
$v=\frac{c}{n}$
refractive index for Bose Einstein condensate is given as
$n=1.57\times10^{7}$
speed of light in vacuum $c=3\times10^8m/s$
speed of light in condensate will be $v=\frac{c}{n}=\frac{3\times10^8m/s}{1.57\times10^{7}}=1.9108\times10m/s$
speed of light in condensate is $v=19.108m/s$
