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Atomic Clocks.

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Atomic Clocks

Name: Wong Yun Sheng Calvin (2O/23)


As pictured above, a scientist stands over a NB-5 atomic clock.

How do atomic clocks work?

Atomic clocks measure time by the frequency of radiation emitted by an atom or molecule when it makes a transition between two energy states. An atomic clock measures the frequency of electromagnetic radiation emitted by an atom or molecule. Atomic clocks are extremely precise and are used to keep universal time—the international basis for establishing legal and scientific times and for setting all public and private clocks worldwide.

When an atom or molecule moves from one energy level to another, a specific amount, or quantum, of energy is absorbed when jumping to a higher energy level or emitted when falling to a lower energy level.

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Atomic clocks determine the frequency of an atom or molecule’s transition in one of two ways. An active atomic clock induces a group of atoms in an elevated energy state to drop to a lower energy state, measuring the frequency of radiation emitted by the atoms. A passive atomic clock exposes a group of atoms in a lower energy state to electromagnetic radiation with changing frequency. When a majority of atoms jump to the next energy level, it signals that the correct frequency has been achieved.

Most atomic clocks in use today are passive cesium clocks. The United States National Bureau of Standards (NBS, now National Institute of Standards and Technology, or NIST) established the second as the time radiation would

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v0 is applied to the beam as it traverses the centre region C, transitions between quantum states will occur. The atoms will then follow the solid lines in the diagram and strike a tungsten-wire detector, which gives electric signals in proportion to the number of cesium atoms striking the wire.

Of course, contrary to popular belief, an atomic clock is NOT the most accurate clock on Earth.  The most accurate clocks on Earth are nuclear clocks, which are able to detect electromagnetic changes of 1/1014, making them 1000 times more accurate than the best atomic clock.

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