Breaking a glass using an electromagnetic wave

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Discussion Overview

The discussion explores the possibility of breaking glass using electromagnetic waves, particularly at resonant frequencies. Participants consider theoretical and practical aspects, including the nature of glass as a dielectric and the implications of resonant versus non-resonant frequencies.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants question whether electromagnetic waves can effectively break glass at its resonant frequency, drawing parallels to resonant sound frequencies.
  • One participant suggests that if the frequency of the electromagnetic wave falls within a range that the glass absorbs, it might be possible to break it through uneven heating and expansion.
  • Another participant notes the difficulty in determining the resonant frequency of crystal, citing variations in lead content and shape as factors that could affect resonance.
  • It is proposed that while breaking glass with electromagnetic waves is theoretically possible, it would require substantial power, and an alternative method could involve using a transparent conductive coating to drive the fundamental frequency.
  • A participant mentions that non-resonant methods for breaking glass are relatively straightforward.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using electromagnetic waves to break glass, with no consensus reached on the effectiveness or practicality of the proposed methods.

Contextual Notes

The discussion highlights uncertainties regarding the resonant frequencies of different types of glass and the power requirements for using electromagnetic waves effectively.

eoghan
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Hi there!
I was wondering: is it possible to break a glass using an electromagnetic wave at its resonant frequency?
 
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Well, I've heard of using resonant sound frequencies to "break a glass"
Not sure about resonant EMF.
 
At first read, I thought it extremely unlikely. EM covers an awful lot of bandwidth, though. Perhaps if the frequency of EM falls within a range that the glass absorbs rather than passing or reflecting, it could work. I don't know enough about it to give a reliable opinion.
 
An EM wave of high enough intensity and at a frequency that the glass absorbs, if dirrected at one part of the glass but not at another will cause uneven heating. This will translate into uneven expansion which can cause cause the glass to break.
 
Uhm.. do you know the resonant frequency of a crystal?
 
eoghan said:
Uhm.. do you know the resonant frequency of a crystal?

I don't think that you can actually determine that other than experimentally. As far as I know, all crystal stemware, ornaments, et al are made of lead crystal. The amount of lead present varies, so it seems to me that the resonance frequency would as well. Also, the specific shape probably makes a difference.
 
Glass is a dielectric, so in principle this should be possible, but would require a substantial amount of power. It would be far easier to electrostatically drive the fundamental frequency of a glass with a thin, even transparent conductive coating.
 
Non-resonant is fairly easy

http://www.thomasnet.com/articles/image/laser-cutting-machine.jpg
 

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