The key difference between dispersion and scattering of light is that dispersion of light is a phenomenon in which the phase velocity of a light wave depends on its frequency, whereas scattering of light is a phenomenon in which moving radiation of light is forced to deviate from a straight trajectory by localized non-uniformities in the medium through which the light pass.
Light is electromagnetic radiation that can show the properties of both waves and particles. It is a form of energy. Dispersion and scattering are two important phenomena that are described regarding light energy.
CONTENTS
1. Overview and Key Difference
2. What is Dispersion of Light
3. What is Scattering of Light
4. Side by Side Comparison – Dispersion vs Scattering of Light in Tabular Form
5. Summary
What is Dispersion of Light?
Dispersion of light is a phenomenon in which the phase velocity of a light wave depends on its frequency. In this definition, the term phase velocity refers to the rate at which the light wave propagates through the medium. The media through which light can disperse are named dispersive media. However, the term dispersion can be used not only with light waves but also with any sort of wave motion, including acoustic dispersion in the case of sound and seismic waves, etc.
Figure 01: Dispersion of Light through a Prism
The most common consequence regarding the dispersion in optics is the change in the angle of refraction of different colours of light. This occurs in the spectrum produced through a dispersive prism and in chromatic aberration of lenses. For example, a rainbow is a result of the dispersion of white light with the spatial separation of white light into its component colours having different wavelengths.
In optical applications, the material dispersion comes as either a desirable or as an undesirable effect where the dispersion of glass prisms can be used to construct spectrometers and spectroradiometers. However, it is important to study dispersion control in lasers that produce short pulses.
What is Scattering of Light?
Scattering of light is a phenomenon in which moving radiation of light is forced to deviate from a straight trajectory by localized non-uniformities in the medium through which the light passes. Scattering can occur with sound waves as well. This process of scattering involves deviation of reflected radiation from the angle that is predicted by the law of reflection. Here, the reflection that occurs regarding radiation is often named as diffused reflections (similarly, the un-scattered reflections are named as specular reflections).
Simply, scattering of light refers to the particle-particle collisions between molecules, atoms, electrons, photons and other particles. An example is the cosmic ray scattering that takes place in the Earth’s upper atmosphere.
Figure 02: Zodiac Light – a diffuse glow visible light in the night sky which is caused by scattering of sunlight by dust particles that are spread through the plane of the solar system.
The different forms of non-uniformities that can cause scattering are named scatterers or scattering centres. Some examples for this type of non-uniformities include particles, bubbles, droplets, density fluctuations in fluids, etc.
The areas where the scattering effect of light has applications include medical applications, semiconductor inspection, polymerization process monitoring, identification of defects in monocrystalline solids, etc.
What is the Difference Between Dispersion and Scattering of Light?
Dispersion and scattering are two important phenomena that take place in media through the media which light can pass. The key difference between dispersion and scattering of light is that dispersion of light is a phenomenon in which the phase velocity of a light wave depends on its frequency, whereas scattering of light is a phenomenon in which moving radiation of light is forced to deviate from a straight trajectory by localized non-uniformities in the medium through which the light pass.
The below infographic shows the differences between dispersion and scattering of light in tabular form.
Summary – Dispersion vs Scattering of Light
The terms dispersion and scattering are discussed regarding moving waves such as light and sound. The key difference between dispersion and scattering of light is that dispersion of light is a phenomenon in which the phase velocity of a light wave depends on its frequency, whereas scattering of light is a phenomenon in which moving radiation of light is forced to deviate from a straight trajectory by localized non-uniformities in the medium through which the light pass.
Reference:
1. “Scattering of Light- Rayleigh Law of Scattering, Types and Examples. “Sciencedoze, 3 Aug. 2020, Available here.
Image Courtesy:
1. “Dispersion of light” By Gagananashree.b1840354 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Zodiacal Glow Lightens Paranal Sky”By ESO/Y. Beletsky – (CC BY 4.0) via Commons Wikimedia