Why as 'second' has been defined in terms of periods of radiation from

1.	Why as 'second' has been defined in terms of periods of radiation from caesium-133?
Answer» Second has been defined in terms of periods of radiation caesium-133, because (i) this period is accurately defined (ii) this period is not affected by changes of place, time and physical conditions like temperature. (iii) the unit is easily reproducible in any good laboratory.

Why as 'second' has been defined in terms of periods of radiation from caesium-133?

Answer»

Second has been defined in terms of periods of radiation caesium-133, because

(i) this period is accurately defined

(ii) this period is not affected by changes of place, time and physical conditions like temperature.

(iii) the unit is easily reproducible in any good laboratory.