The frequency of waves: definition and the ways of calculation

A common concept in physics, waves are described as disturbances that transmit energy through matters and space. Sometimes, they are associated with mass transport, sometimes, they are not. Waves are reported, in physics, at a fixed point, and consist of oscitations or vibrations of a physical field or medium. In physics, there are known two types of waves: mechanical and electromagnetic. While mechanical waves take place in solid, physical matters, electromagnetic waves do not require a physical medium to propagate. They are formed from oscillations of electrical and magnetic fields, periodic ones, generated by particles, and thus, they can also travel through the vacuum. In this category are included radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

Velocity vs. frequency of wavelengths

Another term to describe weaves is frequency. Frequency is usually described as the number of waves passing in a certain unit of time. In wave’s case, the unit used is usually Hertz. The equation for this is one wave per one second, equals a Hertz. As wavelengths increase, the frequency decreases, thus the relationship between the two is an indirectly proportional one.

Many mix wave frequency with wave velocity. However, these two are not even remotely related. Velocity is the same as speed. In the case of many types of waves, the speed is the same for all: 186,000 miles per second. This is described as the speed of light. Frequency is not describing how fast is a wave travelling but how many complete cycles are completed in a certain time unit.

The frequencies of light waves

Now that we know what frequencies are and their relationship with waves, we have to understand the fact that depending on the light, there are various frequencies for each of those.

  • Visible light, usually referred to as colour, is between 430 trillion hertz (red) and 750 trillion hertz (violet).
  • Invisible light – the frequency varies from less than 3 billion hertz to greater than 3 billion hertz (gamma rays).

Everything in between the two above is usually referred to as the electromagnetic spectrum. The first to link the electromagnetic spectrum to electromagnetism is Michael Faraday. He observed that polarized light traveling through transparent materials responds to the magnetic field. This is known as the Faraday Effect.

How to calculate frequencies of light?

Sound, light, and water have all the same frequency and they are calculated based on the same formula. The frequency of light (f) is the number of times a wave’s crest passes a fixed point in a certain time unit, usually second (s). The speed of light is approximately 300,000 km/s and it is noted with a c, usually. The Greek symbol for lambda will represent the wavelength of the wave. You will get the frequency of the light by dividing the speed with which the wave you want to calculate, by the wavelength of the wave in the matter. While there are other formulas based on which you can calculate this, this one is the simplest.