CBSE Class 11-science Answered

The two properties which a standard unit must have are:

1. Invariability - The standard unit must be invariable. That it must not change from time to time and place to place.
If a particular lenght defined as 1 meter at some place than it must be same at any corner of the world, only then it can be accepted as a standard unit.

2. Availability - The standard unit should be easily made available for comparing with other quatities. That it should not be exclusive. It must be availble for comparision with other things so that it can get standardize.

The procedures to define standard units are quite complex and often involve modern equipments. Thus only a brief introduction is given to the procedure.

Hope this helps.
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