SSC MTS EXAM

Detailed explanation-1: -The second, so defined, is the unit of proper time in the sense of the general theory of relativity.

Detailed explanation-2: -The second (s or sec) is the International System of Units (SI) unit of time measurement. One second is the time that elapses during 9, 192, 631, 770 (or 9.192631770 x 109 in decimal form) cycles of the radiation produced by the transition between two levels of the cesium-133 atom.

Detailed explanation-3: -Time is one of the seven fundamental physical quantities in both the International System of Units (SI) and International System of Quantities. The SI base unit of time is the second, which is defined by measuring the electronic transition frequency of caesium atoms.