Difference between absorption and scattering cross sections

In summary, the conversation is about using the Beer-Lambert law to model the attenuation of a weak laser through a gas sample. The speaker is having trouble finding equations for both the scattering and absorption cross sections and is using Loudon's "The Quantum Theory of Light" as a reference. They mention that the book lists an equation for an attenuation coefficient in both chapter 2 and chapter 8, but do not mention an absorption cross section. The speaker also asks about the listener's understanding of cross sections and the difference between scattering and absorption processes. They inquire if the listener wants to understand the concept or just use a model to get a satisfactory answer.
  • #1
Madap
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Hi. I'm trying to model the attenuation (extinction) of a weak laser through a gas sample using the Beer-Lambert law. I've found that the attenuation cross section can be written as the sum of both a scattering and absorption cross section, however I'm having difficulty finding a source that lists equations for both of those.

One book I keep seeing referenced, and have been using myself is Loudon's "The Quantum Theory of Light" . He gives a lot of information, but it's confusing me a little bit. In chapter 2 he lists an equation for an attenuation coefficient, and then in chapter 8 he lists the same equation and calls it the Elastic Raleigh scattering cross section. I haven't seen any mention of an absorption cross section anywhere, so I was wondering where that would fit into this model.
 
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  • #2
Can I ask first if you are comfortable with the idea of a cross section? Do you have a mental schema of any kind for this?
How about the difference between a scattering and absorption process? If not at all that's fine of course, just trying to gauge what you might find obvious and not so obvious. Do you want to understand what you are doing or just use a model to get a satisfactory answer?
 
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FAQ: Difference between absorption and scattering cross sections

1. What is the difference between absorption and scattering cross sections?

Absorption and scattering cross sections are both measurements used in the field of optics to describe how light interacts with a material. Absorption cross section refers to the area of a material that is capable of absorbing light, while scattering cross section refers to the area of a material that is capable of deflecting or scattering light in different directions.

2. How are absorption and scattering cross sections related?

Absorption and scattering cross sections are related in that they both describe the behavior of light interacting with a material. However, they are fundamentally different measurements and cannot be directly compared or converted to each other. Absorption cross section is a measure of the amount of light absorbed by a material, while scattering cross section is a measure of the amount of light scattered by a material.

3. Can a material have both absorption and scattering cross sections?

Yes, a material can have both absorption and scattering cross sections. In fact, most materials exhibit both absorption and scattering behavior to some degree. The amount of each depends on the specific properties of the material and the wavelength of the incident light.

4. How do absorption and scattering cross sections affect the color of materials?

The absorption and scattering cross sections of a material can affect its color by determining which wavelengths of light are absorbed or scattered. When a material absorbs certain wavelengths of light, it appears to be a different color because only certain wavelengths are reflected back to our eyes. Scattering can also affect the color of a material by diffusing the light and changing its perceived color.

5. What factors can influence the absorption and scattering cross sections of a material?

The absorption and scattering cross sections of a material can be influenced by various factors, including the chemical composition of the material, the thickness and density of the material, and the wavelength of the incident light. Additionally, external factors such as temperature, pressure, and the presence of other materials can also affect the absorption and scattering behavior of a material.

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