0.002 cm
Reason —
The value of one main scale division (x) = 1/20 m
The number of divisions on an vernier scale(n) = 25
Using the formula given below,
L.C. = x ÷ n = 1/20 ÷ 25
L.C. = 1/500 cm
⇒L.C.=0.002 cm
Hence, the least count of the microscope is 0.002 cm.