The vernier of a circular scale is divided into `30` divisons, which coincides with `29` main scale divisions. If each main scale division is `(1//2)^@` the least count of the instrument is `(1^@=60')`

Options

A. 10'
B. 0.1'
C. 1'
D. 30'

Answer

C

Explanation

Least count = 1 MSD - 1 VSD
but `30VSD=29MSDrArr VSD=((29)/(30))MSD`
Therefore `L.C=1MSD-(29)/(30)MSD`
`= (MSD)/(30)=(0.5^(@))/(30)=((1)/(60))=1`