In finding out refractive index of glass slab the following observations were made through travelling microscope 50 vernier scale divisions = 49 MSD; 20 divisions on main scale in each cm For mark on paper MSR = 8.45 cm, VC = 26 For mark on paper seen through slab MSR = 7.12 cm, VC = 41 For powder particle on the top surface of the glass slab MSR = 4.05 cm, VC = 1 (MSR = Main Scale Reading, VC = Vernier Coincidence) Refractive index of the glass slab is :
- 1.52
- 1.35
- 1.24
- 1.42
Answer
(4) 1.42
Solution
1 MSD = 120 cm = 0.05 cm, 1 VSD = 4950 0.05 = 0.049 cm
LC = 1 MSD - 1 VSD = 0.001 cm
Reading = MSR + VC LC: R1 = 8.476 cm, R2 = 7.161 cm, R3 = 4.051 cm
Real depth = R1 - R3 = 4.425 cm, apparent depth = R2 - R3 = 3.110 cm
both depths are measured from the top surface (powder particle)
= 4.4253.110 1.42
Answer: (4)