The key difference between Rayleigh and Raman scattering is that the Rayleigh scattering is an elastic scattering whereas the Raman scattering is an inelastic scattering.
Scattering of radiation such as light and sound refers to the derivation of the radiation from a straight flight path due to the non-uniformities of the medium through which the radiation passes. There are two common types of scattering as Rayleigh and Raman scattering. They differ from each other according to the conservation or non-conservation of kinetic energy that we name as either elastic or inelastic scattering respectively.
CONTENTS
1. Overview and Key Difference
2. What is Rayleigh Scattering
3. What is Raman Scattering
4. Side by Side Comparison – Rayleigh vs Raman Scattering in Tabular Form
5. Summary
What is Rayleigh Scattering?
Rayleigh scattering is a form of an elastic scattering of light or any other electromagnetic radiation, named after the scientist Lord Rayleigh (John William Strutt). Elastic scattering means that this form of scattering conserves the kinetic energy of the incidental particles of the system in which the scattering takes place. Therefore, the scattered photons have the same energy as the incident photons.
Figure 01: The blue color of the sky is a result of Rayleigh scattering of light in the atmosphere.
Rayleigh scattering does not change the state of a material. Therefore, we name it as a “parametric process”. The particles involved in this scattering can be atoms or molecules. This type of scattering takes place when light passes through transparent solids and liquids. However, we can see it prominently in gases. This form of light scattering is a result of the polarizability of the particles in the medium through which it passes.
What is Raman Scattering?
Raman scattering is a form of inelastic scattering of light or any other electromagnetic radiation, named after the scientist C.V.Raman. The term inelastic describes that this type of scattering does not conserve the kinetic energy of incidental particles. In other words, the kinetic energy of the system (in which the light scattering takes place) either losses or increases. The particles that involve Raman scattering may be electrons, atoms or molecules. In gases, this type of light scattering occurs with a change in the energy of molecules. This is due to the transition of the molecule from one energy level to another.
What is the Difference Between Rayleigh and Raman Scattering?
Rayleigh scattering is a form of an elastic scattering of light or any other electromagnetic radiation whereas Raman scattering is a form of inelastic scattering of light or any other electromagnetic radiation. Therefore, the main difference between Rayleigh and Raman scattering is their elastic and inelastic nature, respectively. Moreover, based on this main difference, we can deduce another difference between Rayleigh and Raman scattering. That is, the elastic scattering is a form of scattering that conserves the kinetic energy of the incidental particles of the system in which the scattering takes place. But, the inelastic form of scattering do not conserve the kinetic energy of the incidental particles.
The below infographic presents more details on the difference between Rayleigh and Raman scattering.
Summary – Rayleigh vs Raman Scattering
Scattering of electromagnetic radiation is in two common types as Rayleigh and Raman scattering. Even though there are some differences between them, the key difference between Rayleigh and Raman scattering is that the Rayleigh scattering is an elastic scattering whereas the Raman scattering is an inelastic scattering.
Reference:
1. Britannica, The Editors of Encyclopaedia. “Rayleigh Scattering.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 12 Feb. 2018. Available here
2. “Raman Scattering.” Wikipedia, Wikimedia Foundation, 30 Aug. 2018. Available here
Image Courtesy:
1.”Rayleigh sunlight scattering”By Dragons flight (CC BY-SA 3.0) via Commons Wikimedia