How does density affect wave absorption in substances?

Click For Summary

Discussion Overview

The discussion revolves around the relationship between the density of a substance and its ability to absorb energy from waves, including electromagnetic and possibly other types of waves. Participants explore theoretical frameworks, specific laws, and factors influencing absorption, with a focus on high-energy radiation and the role of frequency.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • MarkySims inquires about an equation or formula that links density to wave energy absorption.
  • Claude references Beer's Law as a potential framework, noting that the absorption coefficient depends on the absorption cross section, which is related to density, but emphasizes that this law is applicable only for comparing samples of the same substance.
  • Claude also mentions uncertainty regarding the applicability of Beer's Law to types of waves other than electromagnetic waves.
  • Another participant points out that for high-energy radiation like gamma rays, the situation is more complex due to scattering effects that also influence energy loss.
  • Claude suggests that electronic and rovibrational resonances are significant in determining absorption spectra, with density being a factor primarily when comparing similar substances.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of specific laws and the complexity of absorption phenomena, particularly in the context of high-energy radiation. There is no consensus on a definitive relationship or formula that universally applies across different types of waves and substances.

Contextual Notes

Limitations include the dependence on the type of wave being considered, the specific properties of the substances involved, and the potential for varying absorption mechanisms based on energy levels.

Markysims
Messages
1
Reaction score
0
Hi,
Is there an equation or a formula or ratio or something similar that relates the density of an object to how much it absorbs energy from the wave moving through it?

Thanks

MarkySims
 
Physics news on Phys.org
The closest law I can think of that does this would be Beer's Law.

[tex]A=A_0e^{-\alpha.z}[/tex]

The quantity [itex]\alpha[/itex] depends on the absorption cross section, which is a function of density (I can't think of the exact relation off the top of my head).

Note that such a law could only be used to compare two samples of the same substance as absorption cross section varies from substance to substance.

Regards,
Claude.

Edit - This applies to electromagnetic waves, but I cannot be 100% certain in applied to other types of waves, maybe someone else can clarify this.
 
Last edited:
For very high energy radiation (gamma rays) it is more complicated. In addition to absorption, the gamma rays undergo scattering, which changes the ray direction and also results in a loss of energy. This subject has been heavily investigated and I presume there are tables of the energy attenuation for various substances.
 
I think Plank's constant plays a role here. Because, how much energy is absorbed will depend on the frequency of the wave passing through.
 
Electronic and rovibrational resonances of the substance in question will dominate the absorption spectra, variables like density will probably only be significant when comparing two samples of the same substance.

Regards,
Claude.
 

Similar threads

  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
5K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 21 ·
Replies
21
Views
4K
  • · Replies 17 ·
Replies
17
Views
7K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K