One second is equal to

Options

A. 1650763-73 time periods of Kr clock
B. 652189.63 time periods of Kr clock
C. 1650763.73 time periods of Cs clock
D. 9192631770 time periods of Cs block

Answer

To determine how one second is defined, we can break down the information provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding the Definition of a Second**:
- A second is a unit of time that is defined based on a physical phenomenon.

2. **Reference to Atomic Clocks**:
- The definition of a second is based on the vibrations of atoms. Specifically, it refers to the vibrations of the cesium-133 (Cs-133) atom.

3. **Vibrations of Cs-133**:
- The precise definition states that one second is equal to the time interval of 9,192,631,770 vibrations of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.

4. **Conclusion**:
- Therefore, we conclude that:
\[ 1 \text{ second} = 9,192,631,770 \text{ vibrations of Cs-133 atom} \]