The most common unit used to measure frequency is hertz (Hz), which refers to cycles per second; however, there are some other ways to measure frequency, such as revolutions per minute (RPM) for a motor or beats per minute (BPM) for a person's heartbeat. Frequency refers to how often an event occurs in a specific time frame, such as a minute or second.
Frequency of a sound wave can also be measured by dividing the speed of sound by the wavelength, represented by the Greek letter lambda. Physicists use different methods to calculate the frequency, including a simple counter, a stroboscope, a frequency counter and heterodyne methods. A frequency counter is used to measure electrical waves, while a stroboscope measures the frequency of light waves.
In communications and physics, a person can calculate a wave's frequency to tell how many waves pass by a specific point in a second or hour. One cycle of the repeating movement is referred to as a period. Some other things that have a frequency that can be measured include radio and TV waves, which are often measured in kilohertz (which stands for 1,000 cycles per second) or megahertz (which stands for 1 million cycles per second).