Why doesn't a fluorescent lamp implode and shatter ?

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Discussion Overview

The discussion revolves around the structural integrity of fluorescent lamps in relation to the pressure difference between the inside and outside of the lamp. Participants explore why these lamps do not shatter despite the significant pressure differential, considering factors such as the shape of the lamp and the properties of glass under pressure.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant cites Wikipedia, noting that the pressure inside a fluorescent lamp is 0.3% of atmospheric pressure, leading to a significant pressure difference that could theoretically cause shattering.
  • Another participant argues that the article's reference to glass shattering applies to flat surfaces, suggesting that the curved shape of fluorescent lamps (tubes) provides greater strength.
  • A follow-up question is posed regarding whether a rectangular lamp would shatter, indicating curiosity about the impact of shape on structural integrity.
  • A later reply asserts that a rectangular lamp would likely shatter unless the glass was very thick, emphasizing the strength of curved surfaces in vacuum vessels.

Areas of Agreement / Disagreement

Participants express differing views on the implications of lamp shape on shattering, with some agreeing that curved surfaces are stronger, while others question the effects of different geometries. The discussion remains unresolved regarding the specific conditions under which a fluorescent lamp might shatter.

Contextual Notes

Participants do not fully explore the assumptions regarding glass thickness or the specific conditions that would lead to shattering, leaving these aspects unresolved.

Hurricane939
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Accoring to Wikipedia, the pressure inside a fluorescent lamp is 0.3% of the atmospheric pressure, so the pressure difference between the outside and the inside of the lamp is almost equal to the atmospheric pressure which is 1 bar or 14.7 psi.

Now according to this and this, glass shatters at an overpressure of about 1 psi, and sometimes even less than that.

So why doesn't the difference in pressure between the outside and the inside of a fluorescent lamp cause the glass to shatter ?
 
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The article is referring to windows, which are flat. Arches (tubes)are much stronger.
 
russ_watters said:
The article is referring to windows, which are flat. Arches (tubes)are much stronger.
So if the lamp shape was rectangular for example, would it shatter ?
 
Hurricane939 said:
So if the lamp shape was rectangular for example, would it shatter ?
Yes; unless the glass was very thick. The principle of using curved surfaces for vacuum vessels is pretty universal. CRTs, radio valves, dewar flasks . . . . .
 

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