Q. In an experiment the angles are required to be measured using an instrument. 29 divisions of the main scale exactly coincide with the $30$ divisions of the vernier scale. If the smallest division of the main scale is half-a-degree $( = 0.5{^\circ})$ then the least count of the instrument is
A) One minute
B) Half minute
C) One degree
D) Half-degree
Explanation
$30\ VSD = 29\ MSD$ $1\ VSD = \frac{29}{30}\ MSD$ $L.C.\ = 1\ MSD - 1\ VSD$ $= \ \left( 1 - \frac{29}{30} \right)\ MSD = \frac{1}{30} \times 0.5{^\circ} = 1$ minute
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.