Q: A spherometer has 200 equal divisions marked on the periphery of its disc . On giving five complete rotations , the central screw advances by 5 mm , Least count of spherometer is

(a) 0.001 cm

(b) 0.001 mm

(c) 0.0005 cm

(d) 0.0005 mm

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Ans: (c)

Sol: $ Pitch = \frac{5}{5}mm $

Pitch = 1 mm

$ Least \; count = \frac{Pitch}{200} = \frac{1}{200} mm $

L.C = 0.005 mm = 0.0005 cm