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What is the difference between frequency and wavelength?

The waves are the way in which many natural phenomena are transmitted, such as sound , light or radio waves. These waves can be described through several measures, including frequency, wavelength or energy.

The sound would be a type of mechanical wave , while the visible light, the radio wave or the gamma radiation would be electromagnetic waves . Although the concepts of frequency and wavelength are applied to both types of waves, in this article we will focus on electromagnetic waves.

As we will see below, frequency and wavelength are inversely related : the higher frequency, the shorter the wavelength, and vice versa. But before entering into this relationship, let’s see what an electromagnetic wave looks like .

Definition of electromagnetic wave

The electromagnetic radiation consists of two perpendicular fields, an electric field and a magnetic field. When the radiation moves, the electromagnetic field oscillates and describes a wave in space.

In other words, an electromagnetic wave is defined as the form of displacement of radiation . Unlike mechanical waves, electromagnetic waves can travel in an empty space, while mechanical waves always need a material medium to propagate.

Definition of frequency and wavelength

The oscillations of electromagnetic radiation in space, the wave , is characterized by ups and downs that form ridges at maximums and valleys at minimums. The distance between maxima and minima together with the propagation speed determine the values ​​of frequency and wavelength.

The wavelength is defined as the distance between two consecutive maxima , or more precisely, the distance a wave disturbance travels in the time interval between two maximum peaks of some physical property of the wave.

The frequency , in turn, is defined as the number of waves that pass a point for a period of time , typically for one second.

 

The frequency, therefore, depends on the wavelength and the velocity of propagation . The higher the speed, the greater number of waves will pass through the same point of space every second, and vice versa, the lower the speed of propagation, the lower the frequency.

Frequency and wavelength formulas

Frequency and wavelength are related to each other through the velocity of propagation and this relation is inversely proportional . If the speed remains constant, the frequency is calculated as the propagation speed between the wavelength .

frequency = speed / wavelength

The wavelength is usually represented by the Greek letter lambda (λ) and in the International System of Units it is measured in meters . The frequency is usually represented by the letter v or f and is measured in hertz or cycles per second (Hz).

In light and other electromagnetic waves that propagate at the speed of light ( c ), the frequency would be equal to the speed of light (≈ 3 × 10 8 m / s) between the wavelength:

Formula frequency and wavelength

v = frequency, c = light speed, λ = wavelength

In the same way, if we know the frequency, the wavelength will be equal to the speed of light between the frequency:

Formula frequency and wavelength

For example, a radio wave of 3 m would have a frequency of 100 thousand hertz:

v = 3 × 10 8/3 m = 100 000 000 Hz = 100 kHz (kilohertz)

Summary of differences

As we have seen, the wavelength is the distance between two equivalent points of a wave, which defines 1 wave or 1 oscillation, and the frequency is the number of waves that pass through a point during a period of time.

In this image two waves are represented. The upper one has a longer wavelength than the lower one.

If the two move at the same speed, for example at the speed of light, the top one would be the one with the lowest frequency, since having a longer wavelength, fewer cycles per second will pass through the same point in space.

This causes frequency and wavelength to be inversely proportionally related through the velocity of propagation

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