Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: neilep on 15/03/2007 19:14:50

Title: The thickness of a bubbles ' wall !!
Post by: neilep on 15/03/2007 19:14:50: I tried measuring the thickness of the wall of some bubbles with my calipers but the bubbles kept on bursting !

Now that's a shame because my calipers have a tolerance of .01 of a millimeter...they are......well accurate !!..LOL

So..........how does one measure the width of a bubble wall !! ?

Can you hurry up !!...I'm keeping a bubble aloft in the air till I know how to measure it !!

Les Hugs et les shmisheys !
Title: The thickness of a bubbles ' wall !!
Post by: another_someone on 15/03/2007 19:51:41: My guess would be to measure the interference patterns between the light reflecting off the two surfaces.

If you have a beam of light that partially reflects off the outer surface of the the wall of the bubble, and partially off the inner surface of the bubble, and the thickness of the wall is in the order of the wavelength of the light, then the two halves of the beam (the one bouncing off the inner surface and the one bouncing off the outer surface) will interact to form constructive and destructive interference (this is what causes all the colours you see from the bubble). By measuring the angle at which constructive and destructive interference occur, you could measure the distance between the inner and outer surface of the wall, and thus the thickness of the wall.
Title: The thickness of a bubbles ' wall !!
Post by: neilep on 15/03/2007 20:52:32: Phew !!

THANK YOU George !.....in the absence of such apparatus to perform such a delicate task I will let the bubble go now and put my calipers away.

I wonder if such an experiment has ever been performed ?....do you think the constant flow of the bubble surfaces would effect the results ?.............I imagine the apparatus would be governed to display ' averages '
Title: The thickness of a bubbles ' wall !!
Post by: Soul Surfer on 15/03/2007 22:31:43: If you watch a soap bubble carefully, as the liquid all slowly drains to the bottom or evapoprates and the bubble gets thinner at the top. Initially it is all just transparent and reflects the sky but eventually the film gets thin enough for interference colours to be developed as the thickness approaches the wavelength of light evenually the colours go "black" and non reflective as the thickness gets less than that and sections of the top part of the bubble become invisible. Sometimes it is possible to have only half the bubble visible, like a floating bowl, before the film finally fails and the bubble pops.
Title: The thickness of a bubbles ' wall !!
Post by: Karen W. on 16/03/2007 03:12:35: Hey neil dip the wand and blow a couple bubbles, leaving enough bubble goop to measure the thickness of the remaining soap on the wand..without blowing the last bubble out of the wand. it should give you a close idea, and then determine that would be thinned by perhaps half,in order to expand the bubble! Will that work?? Sort of?
Title: The thickness of a bubbles ' wall !!
Post by: Bored chemist on 16/03/2007 21:50:59: You could get the average thickness by weighing it and calculating from the bubbles diameter and the density of the solution. The film is thicker at the bottom so you would need something more sophisticated to get a true picture. Interferometry would do. Spiking a dye into the solution would let you follow the thickness by light absorbtion.