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JEE Main 202229 JulyMorning Shift

Exam: JEE Main
Year: 2022
Date: 29 July
Shift: Morning Shift
Subject: Physics
Chapter: Experimental Physics

JEE Main 2022 · 29 July · Morning Shift · Physics · Experimental Physics

A travelling microscope has 20 divisions per cm on the main scale...

A travelling microscope has

20

divisions per

cm

on the main scale while its Vernier scale has total

50

divisions and

25

Vernier scale divisions are equal to

24

main scale divisions, what is the least count of the travelling microscope ?

Options

A $0 . 001cm$
B $0 . 002mm$
C $0 . 002cm$
D $0 . 005cm$

Correct answer

C. $0 . 002cm$

Step-by-step solution

One main scale division $MSD = \dfrac{1}{20}cm$
One vernier scale division $VSD = \dfrac{24}{25}MSD = \dfrac{24}{25} \times \dfrac{1}{20}cm$
$∴$ Least count $LC = MSD - VSD = \dfrac{1}{20}\left(1 - \dfrac{24}{25}\right)cm$
$= \dfrac{1}{20} \times \dfrac{1}{25} = \dfrac{1}{500} = 0 . 002cm$
$= 0 . 002cm$

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