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
$Least\ count = \frac{Value\ of\ main\ scale\ division}{No.of\ divisions\ on\ vernier\ scale}$ $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{1}{30}\ MSD = \frac{1}{30} \times \frac{1{^\circ}}{2} = \frac{1{^\circ}}{60} = 1\ \min$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.