JEE Main & Advanced Physics Mathematical Tools, Units & Dimensions JEE PYQ - Mathematical Tools Units and Dimensions

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\[(=0.5{}^\text{o}),\] then the least count of the instrument is: [AIEEE 2009]

A) one minute

B) half minute

C) one degree

D) half degree

Correct Answer: A

Solution :

[a] \[1VSD=\frac{29}{30}MSD\]

\[L.C.=1\text{ }MSD1\text{ }VSD\]

\[=\frac{1}{30}MSD\]

\[=\frac{1}{30}\times 0.5=\frac{1}{60}=one\text{ }minute\]