The Number of Times Per Second That a Wave Cycles: Frequency Explained
Frequency is the number of times per second that a wave cycles — how many complete repetitions pass a fixed point every second. It is measured in hertz (Hz), where 1 Hz equals one full cycle per second.
Frequency Definition Explained
A single cycle is one complete repetition of the wave’s pattern: for a sound wave, one full compression-and-rarefaction; for a light wave, one complete oscillation of the electromagnetic field. Counting how many of those cycles occur in one second gives you the frequency. If a wave completes 50 full cycles each second, its frequency is 50 Hz. Higher frequency means more cycles packed into the same time. As Encyclopaedia Britannica notes, frequency is fundamental to describing any periodic wave, whether it is sound, light, or a radio signal.
Measuring Frequency in Hertz
The hertz is the standard unit, defined as one cycle per second, and it is maintained as part of the International System of Units by bodies such as the National Institute of Standards and Technology. Frequency (f) relates directly to the period (T), the time for one cycle:
- f = 1 / T — a wave with a period of 0.01 seconds has a frequency of 100 Hz.
- For a wave moving at speed v, f = v / λ, where λ (lambda) is wavelength.
A quick example: an AM radio station broadcasting at 1,000 kHz means its carrier wave cycles one million times per second.
Key Takeaways
- Frequency is the number of complete cycles a wave completes each second.
- It is measured in hertz (Hz), where 1 Hz = one cycle per second.
- Frequency and period are reciprocal: f = 1 / T.
- Frequency also relates to wavelength and wave speed through f = v / λ.
