The Naked Scientists

The Naked Scientists Forum

Author Topic: Flash of light when opening envelopes  (Read 14005 times)

Offline MissMontana

  • Sr. Member
  • ****
  • Posts: 114
    • View Profile
Flash of light when opening envelopes
« on: 27/04/2004 21:35:43 »
Has anyone ever opened one of those self-seal envelopes and seen a blue flash?  Can anyone tell me what causes it?


 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Re: Flash of light when opening envelopes
« Reply #1 on: 27/04/2004 21:40:43 »
That's fantastic Toni....yes I've noticed that lots of times.....really really good question !!...I wonder if it's a friction orientated thing ? as the glue is stretched it must cause a radioactive luminescent reaction....not that I understand it, but I hope we get an answer...nice one !!

'Men are the same as women...just inside out !'
 

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5339
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
Re: Flash of light when opening envelopes
« Reply #2 on: 28/04/2004 00:54:29 »
The flash of light you see when opening an envelope, or pulling sticky tape off a surface, is called 'triboluminescence', from the Greek word tribein - to rub - and the Latin word lumin - light.

It is partly a piezoelectric effect - piezoelectric materials generate electricity when they are stretched or squeezed. When you supply energy to the molecules of the glue on the envelope, the disribution of charges changes across the molecule, separating plus and minus. The charges tend to congregate in areas of the molecules containing irregularities or impurities. When a sufficiently large charge difference has accumulated, it 'shorts out' back through the glue. On its way, just like lightning travelling through the air, the electricity excites atoms in the glue which re-release this energy as light.

In simple terms, when the atoms of the glue are excited by the electricity, some of the electrons in the excited atoms temporarily leap up to a higher energy level. When these electrons fall back to their original energy level they release their excess energy as light.

You can even see the same thing with certain foods when you eat them ! Some types of sweets (containing large amounts of sucrose) can produce similar flashes of light in the mouth as you crunch them up.

Happy crunching

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx
 

Offline tweener

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 1144
    • View Profile
Re: Flash of light when opening envelopes
« Reply #3 on: 28/04/2004 03:17:14 »
I can sometimes generate a small electrical storm pulling a sweater off in the dark.  You can hear the crackling (even in the light) and see the tiny flashes all over the place.  This is caused by static electricity, which is when electrons that are loosely bound on one materal get rubbed off on another material.  When enough of them get transferred, the electric field gets large enough to jump the gap.

----
John - The Eternal Pessimist.
 

Offline gsmollin

  • Hero Member
  • *****
  • Posts: 749
    • View Profile
Re: Flash of light when opening envelopes
« Reply #4 on: 28/04/2004 03:47:55 »
That's related. It's called triboelectricity, or more commonly static electricity, although the discharges aren't static. They are called ESD, electrostatic discharge. That is a major problem for electronic equipment. The static field you generate from rubbing clothing together is enough to destroy sensitive MOS devices, like computers. Pulling tape off of a roll or opening the envelope generates ESD, which excites those flashes you saw, and creates a large static field, typically at least 4000 volts.
 

Offline bezoar

  • Hero Member
  • *****
  • Posts: 950
    • View Profile
Re: Flash of light when opening envelopes
« Reply #5 on: 02/05/2004 20:23:01 »
Pop Rocks do it, and so do Wintergreen lifesavers.
 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Re: Flash of light when opening envelopes
« Reply #6 on: 02/05/2004 20:37:45 »
Yayy..I always remember my sister used to have a nightie made out of something (this is probably 35 years ago...cripes !!)...could it have been a nylon thingy ? I remember it being quite soft...(err..not that I wore it of course....well..err !!)...anyway..as per Johns post, the light show was incredible against the blankets that we had then...(of course we all enjoy Duvets now...well..we do anyway !)...

Nancy...isn't a lifesaver a sweet of sorts ? if it is....gosh !!

'Men are the same as women...just inside out !'
 

Offline Donnah

  • Ma-Donnah
  • Neilep Level Member
  • ******
  • Posts: 1756
    • View Profile
Re: Flash of light when opening envelopes
« Reply #7 on: 03/05/2004 19:44:30 »
When I had a mouthful of amalgam fillings it was difficult to eat because I kept getting zapped.  I even picked up a radio station on my teeth one time.  That freaked me out a bit because I didn't know where the voices came from, then the music started and I clued in.  How is that possible though, to become a living radio signal receiver?
 

Offline gsmollin

  • Hero Member
  • *****
  • Posts: 749
    • View Profile
Re: Flash of light when opening envelopes
« Reply #8 on: 23/06/2004 00:50:18 »
Back from the dead,

I was perusing old threads and i found Donnah's great post. Woa Donnah, you lucky girl, you could detect radio signals with your teeth! You know, I tried that lots of times, but I suppose my fillings were too pure.

The detection of AM radio signals requires a device, known as a detector, duh. It is made by placing disimilar conductors in contact. With mercury-silver amalgams, it would be the silver and mercury, of course. There is a small difference in the atomic conduction levels in the two metals, which causes a small potential between them. This can rectify an alternating current, from the RF energy in the radio signal, and produce the baseband audio signal. I was so anxious to hear those radio signals in my head that I even tried aluminum foil against my fillings, but that is really bad karma. So I never had voices in my head:(.
 

Offline OldMan

  • Sr. Member
  • ****
  • Posts: 222
    • View Profile
Re: Flash of light when opening envelopes
« Reply #9 on: 23/06/2004 04:46:39 »
I dont understand how it works to hear radio through fillings when there are no speakers or anything like that.
Donnah if you twisted your teeth could you change stations? :) What a pain if you got stuck on a foreign language channel!

-----------------------------
A prism with an intellect, you throw your light selectively.
 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Re: Flash of light when opening envelopes
« Reply #10 on: 24/06/2004 12:48:27 »
gsmollin...when you put the foil on your fillings didn't it give you a 'zap' ?...also....doesn't something have to vibrate to produce the audio ?...if so...what is vibrating ?...or did you answer that already ?...and can the radio signal be heard by others or just by the person with the fillings ?......

In my never ending quest to assist this great site I attatched an aerial to my mouth and glued a tuning knob to my nose but alas all I can pick up is strange looks !! :D

'Men are the same as women...just inside out !'
 

The Naked Scientists Forum

Re: Flash of light when opening envelopes
« Reply #10 on: 24/06/2004 12:48:27 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums