Difference Between De Broglie Wavelength and Wavelength

The key difference between De Broglie wavelength and wavelength is that De Broglie wavelength describes the wave properties of a large particle, whereas wavelength describes the wave properties of waves.

Generally, the term wavelength refers to the spatial period of periodic waves; in other words, it is the distance over which the wave’s shape repeats. Therefore, we can measure it as the distance between consecutive corresponding points of the same phase on the wave. E.g. two adjacent troughs. Examples of waves include electromagnetic waves, seismic waves, vibration in a guitar string, ripples on the surface of the water, etc. However, particles sometimes act like waves (wave-particle duality). In such occasions, we can measure the wavelength by means of De Broglie wavelength.

CONTENT

1. Overview and Key Difference
2. What is De Broglie Wavelength
3. What is Wavelength
4. Side by Side Comparison – De Broglie Wavelength vs Wavelength in Tabular Form
5. Summary

What is De Broglie Wavelength?

De Broglie wavelength is a concept in chemistry that is useful in determining the wave properties of matter. Matter waves are discussed under quantum mechanics, as an example for wave-particle duality. All matter behaves as both particles and waves. E.g. a beam of electrons can be diffracted similar to a beam of a light wave.

The chemical concept regarding the wave-like behaviour of particles was first proposed by the scientist Louis de Broglie in 1924. Therefore, we can name it as de Broglie hypothesis. Similarly, we can name wavelength of matter waves as de Broglie wavelength, which is denoted by the lambda, λ. This wavelength is given for a particle having a mass as opposed to a massless particle. Moreover, de Broglie wavelength is related to the momentum of the particle that is denoted by p. The relationship between de Broglie wavelength and momentum of the particle is as follows:

            λ = h/p

Here, “h” is the Planck constant. However, the wave-like behaviour of matter was experimentally demonstrated by George Paget Thomson’s metal diffraction experiment. This experiment was confirmed for elementary particles, neutral atoms and even some small molecules.

What is Wavelength?

Wavelength is the spatial period of a periodic wave. In other words, it is the distance over which the wave’s shape repeats. We can observe the wavelength as the distance between consecutive corresponding points of the same phase on the wave. E.g. two adjacent crests, troughs, zero crossings, etc. Moreover, the wavelength is characteristic for both travelling waves and standing waves as well as other spatial wave patterns.

The inverse of the wavelength of a wave gives the frequency of the wave. Therefore, waves having a high frequency have a shorter wavelength and vice versa. We can denote the wavelength by Greek letter lambda, λ.  The wavelength of a wave depends mainly on the medium through which the wave passes—E.g. vacuum, air, water, etc. Moreover, a range of wavelengths or frequencies is called a spectrum.

What is the Difference Between De Broglie Wavelength and Wavelength?

Wavelength is a property of a wave such as an electromagnetic wave. Sometimes, particles also act as waves; here, we can determine the wavelength as De Broglie wavelength. The key difference between De Broglie wavelength and wavelength is that De Broglie wavelength describes the wave properties of a large particle, whereas wavelength describes the wave properties of waves.

Below infographic shows more details of the difference between De Broglie wavelength and wavelength.

Summary – De Broglie Wavelength vs Wavelength

Wavelength is a property of a wave such as an electromagnetic wave. Sometimes particles also act as waves where we can determine the wavelength as De Broglie wavelength. The key difference between De Broglie wavelength and wavelength is that De Broglie wavelength describes the wave properties of a large particle, whereas wavelength describes the wave properties of waves.

Reference:

1. “Deriving the De Broglie Wavelength.” Chemistry LibreTexts, Libretexts, 15 Aug. 2020, Available here.
2. “De Broglie Wavelength.” IOPSpark, Available here.

Image Courtesy:

1. “Wave-particle duality” By Thierry Dugnolle – Own work (CC0) via Commons Wikimedia
2. “Waves in Box” By Badseed working on a raster by Brews_ohare – Own work, vectorizing File:Waves in Box.JPG by Brews_ohare (CC BY-SA 3.0) via Commons Wikimedia