Question

$50$ divisions on the vernier scale coincides with $49$ divisions on the main scale of a vernier caliper. The least count of instrument, if graduation on the main scale is $2mm$, is :

• A. $\frac{1}{25}mm$
• B. $\frac{1}{50}mm$
• C. $\frac{2}{49}mm$
• D. $\frac{1}{49}mm$

Answer 1

The correct option is A $\frac{1}{25}mm$

Given: $50VSD$ $\equiv$ $49MSD$
Hence , $1VSD$ $=\frac{49}{50}$ $MSD$
Least count of the instrument $=MSD-VSD=2(1-\frac{49}{50})$
( $\because$ MSD is given as 2 mm )
Hence, least count of vernier calipers $=2\left(\frac{1}{50}\right)=\frac{1}{25}$ mm