Given,
The refractive index of the glass slab, n=2.31
The refractive index of an object is defined as the ratio of the speed of light in a vacuum to the speed of light in that object.
That is,
[tex]n=\frac{c}{v}[/tex]Where c=3×10⁸ m/s is the speed of light in the vacuum and v is the speed of light in the given block of glass.
On rearranging the above equation,
[tex]v=\frac{c}{n}[/tex]On substituting the known values,
[tex]\begin{gathered} v=\frac{3\times10^8}{2.31} \\ =1.3\times10^8 \end{gathered}[/tex]Thus the speed of light in the given block of glass is 1.3×10⁸ m/s
