Soap bubble

A soap bubble is a very thin soap film of soap water that forms a hollow spherical shape with an iridescence surface. Soap bubbles usually last for only a few moments and burst either on their own or on contact with another object. Due to their fragile nature they have also become a metaphor for something that is attractive, yet insubstantial. They are mostly used as a children's plaything, but their usage in artistic performance shows that they can be fascinating for adults too. Soap bubbles can help to solve complex mathematics problems of space, as they will always find the smallest surface area between point or edge. ==Physics== ===Surface tension and shape=== [[Image:Jean-Baptiste Sim�on Chardin 022.jpg|thumb|Soap bubbles, Jean-Baptiste Sim�on Chardin, 2nd third of 18th century.]] Soap bubbles can exist because the surface layer of a liquid—in this case water—has a certain surface tension, which causes the layer to behave as an elastic sheet. A common misconception is that soap increases the water's surface tension. Actually soap does the exact opposite, decreasing it to approximately one third the surface tension of pure water. Soap does not ''strengthen'' bubbles, it ''stabilizes'' them, via an action known as the Marangoni effect. As the soap film stretches, the concentration of soap decreases, which causes the surface tension to increase. Thus, soap selectively strengthens the weakest parts of the bubble and tends to prevent them from stretching further. In addition, the soap reduces evaporation so the bubbles last longer. Their Sphere shape is also caused by surface tension. The tension causes the bubble to form a sphere, as a sphere has the smallest possible surface area for a given volume. This shape can be visibly distorted by air currents, and hence by blowing. If a bubble is left to sink in still air, however, it remains very nearly spherical, more so for example than the typical cartoon depiction of a raindrop. When a sinking body has reached its terminal velocity, the drag force acting on it is equal to its weight, and since a bubble's weight is much smaller in relation to its size than a raindrop's, its shape is distorted much less. (The surface tension opposing the distortion is similar in the two cases: The soap reduces the water's surface tension to approximately one third, but it is effectively doubled since the film has an inner and an outer surface.) === Freezing === Soap bubbles blown into air that is below a temperature of around 0� Fahrenheit (–15� Celsius) will freeze when they touch a surface. The air inside will gradually diffusion out, causing the bubble to crumple under its own weight. At temperatures below approximately –15� Fahrenheit (–25� Celsius), the bubbles will freeze in the air and shatter when they hit the ground. === Merging ===

When two bubbles merge, the same physical principles apply, and the bubbles will adopt the shape with the smallest possible surface area. Their common wall will bulge into the larger bubble, as smaller bubbles have a higher internal pressure. If the bubbles are of equal size, the wall will be flat. At a point where two or more bubbles meet, they sort themselves out so that only three bubble walls meet along a line, separated by angles of 120�. This is the most efficient choice, again, which is also the reason why the cells of a beehive (beekeeping) use the same 120� angle, thus forming hexagon. Only four bubble walls can meet at a point, with the lines where triplets of bubble walls meet separated by 109.47�. ===Interference and reflection=== The iridescent colours of soap bubbles are caused by interference light waves. As light impinges on the film, some of it is reflection off the outer surface while some of it enters the film and reemerges after being reflected back and forth between the two surfaces. The total reflection observed is determined by the interference of all these reflections. Since each traversal of the film incurs a phase shift proportional to the thickness of the film and inversely proportional to the wavelength, the result of the interference depends on these two quantities. Thus, at a given thickness, interference is constructive for some wavelengths and destructive for others, so that white#White light impinging on the film is reflected with a hue that changes with thickness. A change in colour can be observed while the bubble is thinning due to evaporation. Thicker walls cancel out red (longer) wavelengths, thus causing a blue-green reflection. Later, thinner walls will cancel out yellow (leaving blue light), then green (leaving magenta), then blue (leaving yellow). Finally, when the bubble's wall becomes much thinner than the wavelength of visible light, all the waves in the visible region cancel each other out and no reflection is visible at all. When this state is observed, the wall is thinner than about one millionth of an inch (25 nanometres)—and is probably about to pop. Interference effects also depend upon the angle at which the light strikes the film, an effect called ''iridescence''. So, even if the wall of the bubble were of uniform thickness, one would still see variations of color due to curvature and/or movement. However, the thickness of the wall is continuously changing as gravity pulls the liquid downwards, so bands of colours that move downwards can usually also be observed. == Mathematical properties == Soap bubbles are also physical illustrations of the problem of minimal surfaces, an area of intense mathematical and scientific study over the past 15 years. For example, while it has been known since 1884 that a spherical soap bubble is the least-area way of enclosing a given volume of air (a theorem by Schwarz), it was only recently proved in the year 2000 that two merged soap bubbles provide the optimum way of enclosing two given volumes of air with the least surface area. This has been termed the ''double bubble theorem''. ==How to make soap bubbles == The easiest ways are to use commercially produced soap bubble fluid (marketed as a toy) or to simply put some dish washing soap in water. However, this latter might not work as well as expected, and there are several tricks to improve the soap sud formula: ===Additives=== * Something to reduce the water's surface tension: Liquid soap or baby shampoo. These may work better the more pure (devoid of perfume or other additives) the soap is, or perhaps with more expensive soaps. * Something to thicken the water. Most commonly used is glycerin (available at the pharmacy), which makes the bubbles more colourful, too. Sugar, icing sugar or corn syrup have similar effects. It may be advantageous to dissolve the sugar in hot water. However, the soap sud can also be too thick and heavy, so it is important not to add too much of these thickening substances. *Distilled water. As tap water contains calcium ions, and these bind the soap, distilled water works better. ===Procedure=== * Leaving the soap sud in an open container overnight makes it thicker, too. But again, if the solution becomes too heavy it will be harder to make soap bubbles. * Bubbles or foam on the surface of the soap sud should be avoided by stirring gently, skimming them away or simply waiting until they are gone. * How easy it is to make soap bubbles depends on a vast number of factors. Every soap is different, and environmental conditions influence performance, too. For example, dusty air is unfavourable, and so is wind. Also, the more humid the air is, the better, which means making soap bubbles is easier on rainy days. Altogether, the best procedure for finding the perfect solution is the trial and error method. ===Bubble blowers=== The easiest way is to use one of the plastic blowers that are sold with most commercial soap bubble solutions. However, as the blower's diameter determines the size of the soap bubble it might be necessary to build a blower oneself. Generally, any closed ring structure works. A blower can be made by bending a wire a into loop with a handle, where the wire should be thick enough so the ring remains stiff. It can be improved by wrapping a thread or bandage around the wire so the soap water can stick better to the ring. A "giant bubble" blower, using a cloth loop attached to a plastic wand, with a slide permitting the loop to be gently opened or closed, was popularized by Klutz Press Publishing, which published a bubble-blowing book with the blower attached. Also, bubbles can be blown by using a bubble pipe, which is made of plastic and usually takes the shape of a smoking pipe, but sometimes has multiple bowls instead of just one. The bubble solution is poured into the bowl of the pipe, and then the person puts the mouthpiece in his or her mouth and blows. Bubbles then rise from the bowl. ===Sample formulae=== #General purpose formula: #*²/₃ cup dish washing detergent #*1 gallon water #*2 to 3 tablespoons of glycerin #Another general purpose formula: #*100 g sugar #*2–3 tablespoons salt #*1.4 l water, better distilled water #*150 ml dish washing detergent #*12 ml glycerin #Yet another general purpose formula: #*1 part of washing-up detergent #*2 parts of glycerin #*3 parts of water #For long living bubbles: #*¹/₃ cup commercial bubble solution #*¹/₃ cup water #*¹/₃ cup glycerin #For no-tears soap bubbles: #*60 ml baby shampoo #*200 ml water #* 3 tablespoons corn syrup ==Performance art== Soap bubble performances combine entertainment with artistic achievement. They require a high degree of skill as well as perfect bubble suds. Some artists create giant bubbles or tubes, often enveloping objects or even humans. Others manage to create bubbles forming cubes, tetrahedra and other shapes or sculptures. Bubbles are often handled with bare hands. To add to the visual experience, they are sometimes filled with smoke or helium and combined with laser lights or fire. Soap bubbles can be filled with a flammable gas such as natural gas and then ignited. Of course this destroys the bubble. == See also == Joseph Plateau, formulator of Plateau's laws on the geometry of intersecting soap films, and Plateau's problem. ==References == * [http://www.exploratorium.edu/ronh/bubbles/bubbles.html A more detailed scientific explanation] * [http://www.ugr.es/~ritore/bubble/bubble.htm The proof paper on the Double Bubble Theorem] * A book about soap bubbles and mathematics:
Oprea, John (2000). ''The Mathematics of Soap Films—Explorations with Maple''. American Mathematical Society (1st ed.). ISBN 0-82-182118-0 * Boys, C. V. (1890) ''Soap-Bubbles and the Forces that Mould Them''; (Dover reprint) ISBN 0-48-620542-8. Classic Victorian exposition, based on a series of lectures originally delivered "before a juvenile audience." * Isenberg, Cyril (1992) ''The Science of Soap Films and Soap Bubbles ''; (Dover) ISBN 0486269604. Fluid dynamics Minimal surfaces simple:Soap bubble

Soap bubble

he 'thin film' colouring phenomenon is called Newton's colours, I'm not sure about the history of it, link should be integrated into the paragraph, I tried but my writting didn't look good enough. I think Newton studied it first (hence the name ;), personally I don't know much about it, I rather read about simulations of the graphic effect. ---- ==Suggestions for improvements== Perhaps there should be some mention of antibubbles (bubbles formed by soap in water, instead of air). see www.antibubbles.org I think the physics section could get a lot more technical. Reference to Newton, and other thin film science (such as how optical coatings on lenses reduce reflection using exactly the same principle as the soap bubble colours, would lend the article weight. Having said that many readers don't wan't to wade trough a lot of physics so i suggest putting the physics section at the end. User:Theresa knott 15:34, 9 Mar 2004 (UTC) I'd certainly like to see that. It's an endlessly rich topic. On which I have only vague half-recollected bits of information. I don't see anything about Plateau in the present article. Indeed, am I crazy or is Joseph Antoine Ferdinand Plateau missing from Wikipedia altogether? Interesting guy... did some early cinema-type zoetrope-ish stuff and, if I recall correctly, stared directly at the sun too long, fried his retinas, and went blind. He's here: Joseph Plateau. Now the only puzzle is why a Google search on "wikipedia plateau" didn't find him. I just added links from the Plateau disambiguation page and Joseph Antoine Ferdinand Plateau. Re interference patterns: my wife had noticed as a kid that bubbles develop black spots just before they burst, but had never made the connection with interference... Incidentally, I think the present explanation of why soap makes/stabilizes bubbles is wrong—specifically, the remark about "the surface tension of water is actually too high, causing the bubble to pop instantly." I don't think it's a case of too low or too high, but of a feedback mechanism. The effect of the surfactant is to cause the surface tension to increase as the bubble film thins, pulling water back into the film and thus ''stabilizing'' the bubble. Or maybe it's the other way around. Or something like that. The thing is, I never understood why a surfactant would do that... so I'm not going to stick my neck out and write about it. I'm just waiting for some jerk to complain that the recipes in the article should be moved to Wikibooks and deleted. All together now. In harmony: :I'm forever blowing bubbles :Pretty bubbles in the air; :They fly so high :Nearly reach the sky :Then, like my dreams, they fade and die; :Fortune's always hiding—I've looked everywhere; :I'm forever blowing bubbles, :Pretty bubbles in the air. User:Dpbsmith 00:04, 11 Mar 2004 (UTC) ---- Another thing that should probably be mentioned is that the color affects happen at integer multiplues of the thickness. So when the bubble is say, 700 nm thick, it will be canceling violet and red. User:Jrincayc 13:24, 13 Apr 2004 (UTC) ---- Help! I added a photo I took while doing the dishes, to the Merging subheading. And the formatting is now all outta wack. I tried adjusting the size of the image, and the diagram that immediately preceeds it, but I fear I don't know the ins and outs of Wiki formatting just yet. I just want the text that follows the new image to fall down the page a bit so that the remaining images line up the way they originally did. Can somebody help me out? Thanks. User:TimothyPilgrim 13:06, Jul 28, 2004 (UTC) == Two potential problems == I think there are two errors in the article, but I don't want to change an article that's already been vetted for featured-article status without discussion. *Water droplets are drop-shaped because of air resistance (drag (physics)), not gravity. In free fall in a vacuum they would be spherical, whereas moving through air in the absence of gravity they would be drop-shaped. The same would be true for soap bubbles, except of course those wouldn't exist if there were no air. That they are almost spherical is due to the much lower terminal velocity at which they travel through the air, compared to water droplets. This of course has to do with their weight, but air resistance is the primary cause for the drop shape; gravity is only a secondary cause, being one way to set things in motion through air. *The article says that the interference comes about because the internally reflected ray travels longer. This explains only the changes in interference due to thickness; the "baseline" for these changes, the complete cancellation in the limit of vanishing thickness, is due to a 180° phase jump in the outer reflection. User:Fpahl 00:26, 22 Sep 2004 (UTC) *You are completely right and should just wikipedia:be bold and edit the article. To be honest I'd forgotton about the phase shift when n₁ < n₂. I'll tell you what - you fix the article and i'll fix the diagrams. User:Theresa knott User talk:Theresa knott 13:18, 22 Sep 2004 (UTC) **Now that's what I call division of labour :-). I'll do that. User:Fpahl 10:40, 23 Sep 2004 (UTC) **OK, I've done the gravity bit. I'll do the reflection bit tomorrow. I don't think the images need any changing, actually, since they only show phase relations for finite path length differences. The captions do, but I can do that together with the text. Speaking of the images, there's a little red squiggle underneath one of the '1's in the upper diagram. And I don't understand the meaning of the white and green circle connected by a line in the lower one. User:Fpahl 14:23, 25 Sep 2004 (UTC) **I've now changed the bit about interference. There was a further problem with it: The cancellation is due not just to two reflections, but to a whole series of them. I've tried to explain this without going into mathematical details. The image captions are now completely out of tune with the text, but I haven't changed them yet since Theresa is deciding whether to change the diagrams themselves. User:Fpahl 12:48, 1 Oct 2004 (UTC) ***I'd suggest deleting them until they are fixed. They're confusing at the moment. User:Filiocht 12:55, 1 Oct 2004 (UTC) ****I will definately amend the images this weekend come hell or high water. The problems you describe false articfacts created when I bodged the drawing :-( they will be easy to remove. User:Theresa knott User talk:Theresa knott 13:02, 1 Oct 2004 (UTC) *****I finally fixed the two images. (you may need to refresh your cache in order to see it) I'm working on two more, one to show the phase relationships, one to show an infinite number of reflections.User:Theresa knott User talk:Theresa knott 20:00, 5 Oct 2004 (UTC) Right here is the first diagram. I've ignored refraction effects to concentrate on the phases of the two reflected rays. I've also ignored all other reflections etc and only concentrated on the two we are actually interested in. Thoughts anyone? :Can you do them so that the sine waves are at zero amplitude at the reflection points? It might be a little clearer what's happening. :User:Wwoods 04:03, 6 Oct 2004 (UTC) I fixed some typos and other small problems in the captions above. I'm in two minds about this use of only two rays. On the one hand, this might make it easier to understand the basic idea. On the other hand, it's really misleading. At shallow incidence, when the reflectivity is high, the second reflection is very insignificant compared to the first, and it's only the long train of later reflections that cancels the first. The images create the false impression that the second ray has the same amplitude as the first. Also, in the left-hand case, where the second reflection is in phase with the first, due to a path-length difference of 180°, the subsequent reflections alternate in phase. I'm aware that all this is very hard to explain in an image, but I don't want people to take away an oversimplified impression of there being cases where the interference is fully constructive or fully destructive. In case it's of any help, here are the details of the mathematics. Denoting the factor by which the amplitude gets multiplied upon the exterior reflection by

r

, we have the following factors: :

r

for the exterior reflection :

1 + r

for transmission into the film :

-r

for each internal reflection :

1 - r

for transmission out of the film Also we incur some phase factor

\Delta

for each traversal of the film. Then we get the following series for the sum of the amplitudes of the ''transmitted'' rays:

(1 + r) \Delta (1 - r) + (1 + r) \Delta (-r) \Delta (-r) \Delta (1 - r) + \ldots

=(1 + r) (1 - r) \Delta (1 + (\Delta r)^2 + \ldots)

=(1 - r^2)\Delta / (1 - (\Delta r)^2)

Taking the squared magnitude of this yields the total transmittance. The phase factor

\Delta

doesn't change the magnitude, so with

\Gamma = \Delta^2

, the phase factor incurred by a double traversal of the film, and with

R = r^2

, the reflectance of a single interface, we get the total transmittance

\left|\frac{1 - R}{1-R\Gamma}\right|^2

The total reflectance is just one minus this; it could also be obtained by summing the amplitude factors of the ''reflected'' rays:

r + (1 + r)\Delta(-r)\Delta(1 - r) + (1 + r)\Delta(-r)\Delta(-r)\Delta(-r)\Delta(1 - r) + \ldots

=r + (1 - r^2) (-r) \Gamma (1 + r^2\Gamma + \ldots)

=r - r \Gamma (1 - r^2) / (1 - r^2\Gamma)

Here the first

r

represents the exterior reflection, and the other term represents the sum of all subsequent reflections. Since the exterior reflection doesn't suffer the

1 - r^2

attenuation from the two transmission processes (which is very significant at high reflectances), it forms a term by itself, whereas the second reflection contributes the first term in a geometric series whose sum at high reflectances is much larger than just the second reflection. I hope that was sort of clear... User:Fpahl 03:10, 7 Oct 2004 (UTC) == Glue-based bubbles? == How do you call that organic solvant-based yellowish or brownish glue in English? There are some people who use this gue to blow large and durable bubbles. It's actually a dangerous glue that you don't want to inhale. Makers of that glue have to add mustard oil in it to stop kids from inhalation. -- User:Toytoy 08:31, Jan 1, 2005 (UTC)

See other meanings of words starting from letter:

S

SB | SC | SD | SE | SF | SG | SH | SI | SJ | SK | SL | SM | SN | SO | SP | SR | SS | ST | SU | SW | SX | SY | SZ |

Words begining with Soap_bubble:

Soap_bubble
Soap_bubble
Soap_bubbles