Atomic clock

High school (ages 12+)
Science & Technology

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/atomic-clock

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the principle of operation?Measures time by counting the resonant frequencies of atomic transitions
2. What is the primary standard element?Cesium-133, with a transition frequency of 9,192,631,770 Hz
3. What is an atomic clock and how does it keep time so accurately?An atomic clock uses atoms and their special energy levels. When an atom jumps between two levels, it emits or absorbs light at a very exact frequency. That frequency is the same no matter the temperature or pressure, so the clock can count time with incredible precision.
4. Why do atomic clocks use cesium-133 and what is special about its frequency?Cesium-133 has a hyperfine transition that produces a microwave frequency of exactly 9,192,631,770 cycles per second. This number is so stable that it defines the length of one second for the whole world.

Quantum Mechanics: The branch of physics that describes the behavior of matter and energy at the atomic and subatomic levels.
Hyperfine Transition: A small energy difference within an atom's ground state, used for precise frequency measurement.
Metrology: The scientific study of measurement, including the units, systems, and methods of measurement.
Terahertz (THz): A unit of frequency equal to one trillion hertz (cycles per second).