JEE MAIN - Physics (2022 - 29th July Morning Shift - No. 18)
A travelling microscope has 20 divisions per $$\mathrm{cm}$$ 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?
0.001 cm
0.002 mm
0.002 cm
0.005 cm
Explanation
1 MSD = $${1 \over {20}}$$ cm
1 VSD = $${{24} \over {25}} \times {1 \over {20}}$$ cm
$$\therefore$$ Least count = 1 MSD $$-$$ 1 VSD
$$ = {1 \over {20}}\left( {1 - {{24} \over {25}}} \right)$$ cm
$$ = {1 \over {20}} \times {1 \over {25}}$$ cm
$$ = 0.002$$ cm
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