The value is one smallest main scale division is divided by total number of vernier scale division is called the least count of vernier caliper.
\( \text { Least count } =\frac{\text { The value of one smallest main scale division }}{\text { Totalnumber of vernier scale division }}\)
\( \\ \text { L.C } =\frac{1 \mathrm{~mm}}{10}=0.1 \mathrm{~mm}=0.01 \mathrm{~cm}\)

The measuring unit of the thickness of a plastic carry bag is micron.

i) Standard units give the correct and accurate measurement like length, mass, time etc...
ii) It is not varied from person to person, place to place and object to object. So we need standard unit.

1. The units named after scientists are not written with a capital intial letter.
Ex: newton, henry, ampere and watt
2. The symbols of units named after scientists should be written by the initial capital letter.
Ex: N for newton, H for henry, A for ampere and W for watt.
3. Small letters are used as symbols for units not derived from a proper noun.
Ex: m for metre, kg for kilogram
4. No full stop or other punctuation marks should be used within or at the end of the symbols.
Ex: 50 m and not as 50 m.
5. The symbols of the units are not expressed in plural form.
Ex: 10 kg not as 10 kgs.
6. Accepted symbols should only be used.
Ex: ampere should not be written as amp and second should not be written as sec.