A spectrometer gives the following reading when used to measure the angle of a prism.
Main scale reading : `58.5 degree`
Vernier scale reading : `09` divisions
Given that `1` division on main scale correspods to `0.5` degree. Total divisions on the vernier scale is `30` and match with `29` divisions of the main scale. the angle of the prism from the above data:

Options

A. 59 degree
B. 58.59 degree
C. 58.77 degree
D. 58.65 degree

Answer

D

Explanation

`1 VSD = (29)/(30)xx0.5^(@) = ((29)/(60))^(@)` and
`1 MSD = ((1)/(2))^(@)=((30)/(60))^(@)`
Least count `= 1 MSD - 1 VSD = ((1)/(60))^(@)`
Reading `= 58.5^(@)+9x((1)/(60))^(@)=58.65^(@)`.