A second is defined as the duration of vibration of:
Correct answer: B. Caesium atom
- A. Carbon atom
- B. Caesium atom
- C. Radium atom
- D. Nitrogen atom
Explanation
B is the correct answer. The current definition of a second is based on the vibrations associated with the caesium-133 atom. The International System of Units (SI) defines a second as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium-133 atom.
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About Measurements
Physical quantities are expressed with SI base and derived units, while measurement limits are described through accuracy, precision, absolute and percentage error, and significant figures. Dimensional analysis checks equations, derives relationships and detects inconsistent units, but it cannot determine numerical constants or distinguish quantities with identical dimensions.
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