Given:

Speed of light in air ( c ) : \(\rm 3 × 10^{8} m/s \)

Speed of light in glass ( v ) : \(\rm 2 × 10^{8} m/s\)

The refractive index of glass with respect to air ( \(\rm µ \) ) is given by:

\(\rm µ \)= $\frac{c}{v}$

\(\rm or,\)\(\rm µ \)= $\frac{3 × 10^{8}}{2 × 10^{8}}$

\(\rm or,\)\(\rm µ \) = $\frac{3}{2}$

\(\rm or,\)\(\rm µ \) = \(\rm 1.5 \)

Thus, the refractive index of glass with respect to air is 1.5.