A vernier has 10. divisions and they are equal to 9 divisions of main scale in length. If the main scale is calibrated in mm, what is its least count?
A
0.1 mm
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B
0.1 cm
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C
0.9 mm
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D
0.9 cm
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Solution
The correct option is A 0.1 mm
Least count can calculated using the formula.
LeastCount=Lengthof1MSD–LengthofIVSD
Where MSD and VSD refer to Main Scale Division and Vernier Scale Division respectively. Here 10 divisions on main scale coincide with 9 divisions on vernier scale.
So, 1VSD is equivalent to 0.9 main scale divisions.
Using the formula for Least Count, we get LC=1MSD–1VSD=1MSD–0.9MSD=0.1MSD=0.1×1mm=0.1mm