How atomic clock works?
Atomic clocks work by keeping time using atoms.
One popular design uses atoms of an isotope of caesium, Cs-133.
The International Committee for Weights and Measures first used it in 1967 to define the duration of one second.
India also uses a Cs-133 atomic clock to define the second for timekeeping within its borders.
Cs-133 is a highly stable atom and is found naturally, which is why it is so commonly used in atomic clocks.
Atomic clocks exploit a fundamental property of all atoms: their ability to jump between different energy levels.
Energy levels are like the steps of a ladder. An atom climbs up the ladder by absorbing energy, like electromagnetic radiation.
In a Cs atomic clock, the energy needed for the atom to jump to a higher energy level matches the frequency of microwave radiation.
This frequency is related in some fully understood way to the duration of a second.
The accuracy of atomic clocks comes from a feedback mechanism that detects any changes in the resonance frequency and adjusts the microwave radiation to maintain resonance.
Thus, a caesium atomic clock loses or gains a second every 1.4 million years.
Optical atomic clock
Optical atomic clocks are even more accurate.
While they have the same working principle, the resonance frequency here is in the optical range.
Radiation in this range includes visible light (to humans) and ultraviolet and infrared radiation.
As part of an optical atomic clock, researchers use lasers to stimulate atomic transitions.
The lasers’ light is highly coherent: the emitted light waves all have the same frequency and their wavelengths are related to each other in a way that doesn’t change.
The result is light with more precise properties and great stability.
The most commonly used atom in optical atomic clocks is strontium (Sr): it has narrow linewidths and stable optical transitions.
Applications
The development of atomic clock is a necessary first-step for their use for navigation, maritime communication, and scientific research.
For example, they can now help monitor underwater seismic and volcanic activity with great precision.
Onboard spacecraft, they can help scientists conduct experiments that test the theories of relativity and potentially reduce the cost of satellite-based navigation.
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