Experimental Skills (Physics) · Question 3

For the determination of refractive index of glass slab, a travelling microscope is used whose main scale contains 300 equal divisions equal to 15 cm. The vernier scale attached to the microscope has 25 divisions equal to 24 divisions of main scale. The least count (LC) of the travelling microscope is (in cm) :

1. 0.002
2. 0.0025
3. 0.0005
4. 0.001

Answer

(1) 0.002

Solution

Value of one main scale division:

1 MSD = 15300 = 0.05 cm

25 VSD = 24 MSD

1 VSD = 2425 MSD

LC = 1 MSD - 1 VSD = 125 MSD

LC = 0.0525 = 0.002 cm

Answer: (1)