Question

Name the physical quantity whose S.I unit is hertz.

Answer 1

The S.I unit hertz is named after the German physicist Heinrich Hertz who was the first to conclusively prove the existence of electromagnetic waves. The S.I unit hertz is the unit of the number of cycles per second.

Complete solution:
Based on the definition of one hertz, guess the physical quantity it represents.
The number of cycles or more generally, the number of occurrences of an event per second is expressed in the unit of hertz. So one hertz indicates that an event repeats itself once every second. Now the number of times an event repeats in a given time is often referred to as the frequency of that event. The frequency is denoted by $\nu$ . So we can conclude that the S.I unit hertz, abbreviated as Hz, is the S.I unit of frequency.

Additional information: Frequency is mainly involved in cyclical processes. Some examples of cyclical processes are oscillation of a body, rotation of a body or waves. Hertz thus can also be defined as the revolutions per second. We define frequency based on the process it represents. When we say the frequency of the water waves while taking a bath is $2{\text{Hz}}$ , the cyclic process under consideration here is waves.

Note: The duration of one cycle is referred to as the period of that cycle and the period will have the dimension of time and the S.I unit of second. So the frequency $\nu$ of that cycle is merely the reciprocal of the period $T$ of the cycle and is given by, $\nu = \dfrac{1}{T}$ . The S.I unit of frequency called hertz will thus be inverse-second i.e, $1{\text{Hz}} = \dfrac{1}{{\text{s}}} = 1{{\text{s}}^{ - 1}}$ .