The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (10 Hz, kHz), megahertz (10 Hz, MHz), gigahertz (10 Hz, GHz), and terahertz (10 Hz, THz). 

Some of the unit's most common uses are in the description of sine waves and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the speeds at which computers and other electronics are driven. 

The hertz is equivalent to cycles per second, i.e., "1/second" or formula_1. The International Committee for Weights and Measures defined the second as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom" and then adds the obvious conclusion: "It follows that the hyperfine splitting in the ground state of the caesium 133 atom is exactly 9 192 631 770 hertz, ν(hfs Cs) = 9 192 631 770 Hz." 

In English, "hertz" is also used as the plural form. As an SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10 Hz), MHz (megahertz, 10 Hz), GHz (gigahertz, 10 Hz) and THz (terahertz, 10 Hz). One hertz simply means "one cycle per second" (typically that which is being counted is a complete cycle); 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. The occurrence rate of aperiodic or stochastic events is expressed in reciprocal second or inverse second (1/s or s) in general or, in the specific case of radioactive decay, in becquerels. Whereas 1 Hz is 1 cycle per second, 1 Bq is 1 aperiodic radionuclide event per second. QUESTIONS:

Q1:
1. What is a hertz in the International System of Units?
2. A hertz in the International System of Units is what?
3. 
Q2:
1. What is the hertz unit most commonly used to describe?
2. What is most commonly described by the hertz unit?
3. 
Q3:
1. is the Hertz unit used to measure anything other than sine waves?
2. Are there any measurements for which the Hertz unit is used other than sine waves?
3. 
Q4:
1. What is the Hertz unit also used for other than measuring sine waves?
2. The Hertz unit is also used for what other application other than sine wave measurement?
3. 
Q5:
1. Where does the Hertz unit get its name from?
2. What is the origin of the Hertz unit's name?
3. 
Q6:
1. What is Heinrich Rudolf Hertz known for?
2. What do people know Heinrich Rudolf Hertz for?
3. 
Q7:
1. Is the Hertz unit only used in English-speaking countries?
2. Are English-speaking countries the only countries that use the Hertz unit?
3. 
Q8:
1. How do you know that the Hertz unit is used in countries that do not speak English?
2. What reason do you have for knowing that the Hertz unit is used in non English-speaking speaking countries?
3. 
Q9:
1. What unit of time is used when defining a Hertz?
2. A Hertz is defined by what unit of time?
3. 
Q10:
1. What is the duration of a second?
2. How is the duration of a second defined?
3. 
Q11:
1. What is the name of the organization that decided on the definition of a second?
2. The definition of a second was decided by which organization?
3. 
