Frequency is a measure of how often something occurs. In terms of waves, frequency is the number of times a wave repeats itself over a given period of time. The higher the frequency, the more times the wave repeats itself and the higher its pitch will be.
From a human perspective, frequency determines what we can hear and how well we can hear it. Our ears are most sensitive to frequencies between the 2-4 kHz range. The human ear can hear sounds with frequencies between 20 Hz and 20,000 Hz (20 kHz).
In terms of electromagnetic waves, frequency is the number of times per second that a wave oscillates, or vibrates. Frequency is measured in hertz (Hz), which is equal to one cycle per second.
From a physics standpoint, frequency has an important role in determining wave properties such as wavelength and amplitude. The frequency of an electromagnetic wave determines its wavelength. Wavelength and frequency are inversely proportional; as one decreases, the other increases. This relationship between wavelength and frequency is known as the Wave Equation.
Electromagnetic waves with frequencies lower than visible light are called “infrared” (IR) radiation. Those with frequencies higher than visible light are called “ultraviolet” (UV) radiation. X-rays and gamma rays have even higher frequencies.