Question

A travelling microscope is used to determine the refractive index of a glass slab. If 40 divisions are there in 1 cm on main scale and 50 Vernier scale divisions are equal to 49 main scale divisions, then least count of the travelling microscope is _______× 10-6 m.

Answer 1

The correct answer is 5 × 10–6 m
Given : 40 M = 1 cm
⇒ M = 0.025 cm ………..(1)
And also, 50 V = 49 M
⇒ Least count = M – V
$= M - \frac{49}{50} M$
$= \frac{M}{50}$
$⇒ LC = \frac{0.025}{50} cm$
$= \frac{250}{50} × 10^{-6} m$
⇒ LC = 5 × 10–6 m