SSC MTS EXAM

Detailed explanation-1: -The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency Cs, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s–1.

Detailed explanation-2: -The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as 1⁄86400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each (24 × 60 × 60 = 86400).

Detailed explanation-3: -Second is the SI unit of time. It is denoted by ‘s’. One second is defined as the time that elapses during 9192631770 cycles of the radiation produced by the transition between two levels of cesium 133 atoms.