In finding out refractive index of glass slab the following observations were made through travelling microscope 50 vernier scale division =49 MSD;…

In finding out refractive index of glass slab the following observations were made through travelling microscope $\displaystyle 50$ vernier scale division $\displaystyle =49 \mathrm{MSD}$; $\displaystyle 20$ divisions on main scale in each cm For mark on paper $$\text { MSR }=8.45 \mathrm{~cm}, \mathrm{VC}=26 $$ For mark on paper seen through slab $$\mathrm{MSR}=7.12 \mathrm{~cm}, \mathrm{VC}=41 $$ For powder particle on the top surface of the glass slab $$\mathrm{MSR}=4.05 \mathrm{~cm}, \mathrm{VC}=1 $$ (MSR = Main Scale Reading, VC = Vernier Coincidence) Refractive index of the glass slab is :