What allows certain wavelengths to pass through walls ?

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Discussion Overview

The discussion revolves around the question of why certain wavelengths of electromagnetic radiation, such as radio waves and X-rays, can pass through walls or body tissue, while visible light cannot. The scope includes theoretical explanations and conceptual clarifications regarding the interaction of different wavelengths with materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that radio waves and X-rays can penetrate walls and body tissue, while visible light is blocked, prompting questions about the underlying reasons.
  • One participant challenges an explanation found in an external article, arguing that it incorrectly describes the speed of electromagnetic radiation and the interaction of wavelengths with matter.
  • Another participant suggests that the interaction of visible light with materials may be due to its wavelength being on a similar scale to the electronic configurations of those materials, leading to higher probabilities of interaction.
  • There is a mention of photoionization cross sections and how increasing photon energy does not always correlate with increased interaction probability, indicating a complex relationship between wavelength and material properties.

Areas of Agreement / Disagreement

Participants express disagreement regarding the explanations provided in an external source, with some participants correcting perceived errors. However, there is no consensus on a definitive explanation for the observed phenomena.

Contextual Notes

Some limitations include the potential misunderstanding of terms such as "speed" versus "frequency" in the context of electromagnetic radiation, and the complexity of interactions between photons and electrons that may not be fully resolved in the discussion.

quickAndLucky
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Radio waves can go through walls and x Rays go through body tissue but the visible spectrum is blocked by both . Why is this the case?
 
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mrnike992 said:
http://www.physlink.com/Education/AskExperts/ae175.cfm

There are problems with his explanation, not the least being

The reason why visible light can't travel through walls as easily as gamma rays or radio waves is because, to the visible light, there's something 'there' on a similar scale of length (wavelength) and time (frequency) that the gamma rays are too small and fast to interact with and the radio waves are too large and slow to interact with.

This is incorrect ... ALL electromagnetic radiation travels at the speed of light
radio waves are NOT slow, gamma rays are NOT fast

he repeats this error several timesDave
 
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Good catch. I was in a hurry earlier, and admittedly, I didn't read the article.
 
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no probs

overall his explanation is pretty poor ... wonder if between us we can find something better for the OP ? :smile:

I know of a good link that explains why glass is transparent to light ... the principles are
going to be similar for other portions of the EM spectrum, I suspect ... am not an expert
in that area of physics :smile:Dave
 
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I'll definitely get looking
 
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davenn said:
radio waves are NOT slow, gamma rays are NOT fast
Dave

I'm guessing the author meant the frequency, not the propagation speed.

I asked my professor something similar about photoionization cross sections ... i.e. increasing photon energy does not always mean an increased cross section. The reasoning he gave was along the lines of the wavelengths become too different for the photon and electron's orbit to interact.

so it could be the case that the visible spectrum interacts with common electronic configurations and is thus blocked (high probability anyway) ... this also explains why it is visible (because it interacts!)
 

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