Answer:
Step-by-step explanation:
a ) one vernier scale division = 19/20 mm.
Least count of vernier scale
= one main scale division - one vernier scale division
= ( 1 - 19 / 20) mm
= .05 mm
b ) uncertainty in the instrument = .05 mm / 1 mm
= 5 %
c ) When the zero mark of the vernier scale does not correspond to the zero
mark of the main scale then there is likelihood of error creeping in the reading by the scale. It is called zero error.