Frequency is measured using a unit called the hertz to denote the number of cycles a wave produces in a second. The number of hertz is calculated by dividing the number of repeat cycles by the length of time in seconds.
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.