why do we read the vernier scale from the point it coincides multiplied by least count

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why do we read the vernier scale from the point it coincides multiplied by least count

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Answer 1

https://en.wikipedia.org/wiki/Vernier_scale#/media/File:VernierscaleHow_a_vernier_scale_works.gif

This gif is a good visual.

Let’s say the accurate measurement is 5.5mm. Each tick on the vernier scale is in this example 0.9mm. Since the actual length is 5.5mm, we’d expect the “.5” tick on the vernier scale to line up best. This is because we start from 5.5, at the 0 tick, then go to 6.4(1) 7.3(2) 8.2(3) 9.1(4) and then 10.0(5).

If the actual measurement were 4.4, then we’d get 4.4(0) 5.3(1) 6.2(2) 7.1(3) 8.0(4), and since the 4th line is lining up best, we add 0.4mm to the 4mm measurement.