Q 11-01-156JEE MainJEE Main 2022 (26 Jun, Shift 2)Easy
A travelling microscope is used to determine the refractive index of a glass slab. If $40$ divisions are there in $1\ \text{cm}$ on the main scale and $50$ vernier scale divisions are equal to $49$ main scale divisions, then the least count of the travelling microscope is ______ $\times10^{-6}\ \text{m}$.
Numerical value type. Enter your answer.
Answer: 5
$1\ \text{MSD} = \dfrac{1\ \text{cm}}{40} = 0.25\ \text{mm}$, $1\ \text{VSD} = \dfrac{49}{50}\ \text{MSD}$.
$$\text{LC} = \frac{1}{50}\ \text{MSD} = \frac{0.25}{50}\ \text{mm} = 0.005\ \text{mm} = 5\times10^{-6}\ \text{m}$$
Solution by Sreeraj P, M.Sc Physics