- Liquid bubble
A bubble is a globule of one substance in another, usually
gas in aliquid . Due tosurface tension , bubbles may remain intact when they reach the surface of the immersive substance.Common examples
Bubbles are seen in many places in everyday life, for example:
* As spontaneousnucleation of supersaturatedcarbon dioxide insoft drink s
* Aswater vapor in boiling water
* Asair mixed into agitated water, such as below a waterfall
* As sea foam
* As given off in chemical reactions, e.g. baking soda + vinegar
* As a gas trapped inglass during its manufacturePhysics and chemistry
Bubbles form, and coalesce into globular shapes, because those shapes are at a lower energy state. For the physics and chemistry behind it, see
nucleation .Appearance
Humans can see bubbles because they have a different
refractive index (IR) than the surrounding substance. For example, the IR of air is approximately 1.0003 and the IR of water is approximately 1.333.Snell's Law describes how electromagnetic waves change direction at the interface between two mediums with different IR; thus bubbles can be identified from the accompanyingrefraction andinternal reflection even though both the immersed and immersing mediums are transparent.One should note that the above explanation only holds for bubbles of one medium submerged in another medium (e.g. bubbles of air in a soft drink); the volume of a
membrane bubble (e.g. soap bubble) will not distort light very much, and one can only see a membrane bubble due tothin-film diffraction andreflection .Applications
Nucleation can be intentionally induced, for example to create
bubblegram art.tHThe bubble is sometimes a triangle a square or a rectangle. They can't be poped because they are really made out of concretePulsation
When bubbles are disturbed, they pulsate (that is, they
oscillate in size) at theirnatural frequency . Large bubbles (negligiblesurface tension andthermal conductivity ) undergoadiabatic pulsations, which means that no heat is transferred either from the liquid to the gas or vice versa. The natural frequency of such bubbles is determined by the equation: [Minnaert, Marcel, On musical air-bubbles and the sounds of running water, Phil. Mag. 16, 235-248 (1933).] Leighton, Timothy G., The Acoustic Bubble (Academic, London, 1994).]:
where:
* is the specific heat ratio of the gas
* is thesteady state radius
* is the steady statepressure
* is themass density of the surrounding liquidSmaller bubbles undergo
isothermal pulsations. The corresponding equation for small bubbles of surface tension σ (and negligible liquidviscosity ) is:
Excited bubbles trapped underwater are the major source of liquid
sound s, such as when arain droplet impacts a surface of water. [cite journal
last = Prosperetti
first = Andrea
coauthors = Oguz, Hasan N.
year = 1993
title = The impact of drops on liquid surfaces and the underwater noise of rain
journal = Annual Review of Fluid Mechanics
volume = 25
pages = 577–602
doi = 10.1146/annurev.fl.25.010193.003045
url = http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.fl.25.010193.003045
format =PDF
accessdate = 2006-12-09 ] [cite web |url=http://ffden-2.phys.uaf.edu/311_fall2004.web.dir/Ryan_Rankin/bubble%20resonance.htm |title=Bubble Resonance |accessdate=2006-12-09 |last=Rankin |first=Ryan C. |year=2005 |month=June |work=The Physics of Bubbles, Antibubbles, and all That]See also
*
Sonoluminescence
*Bubble fusion
*Underwater acoustics References
External links
* [http://www.physicstoday.org/pt/vol-56/iss-2/p36.html Bubble physics] – touches on vapor pressure, bubble formation, bubble dynamics, cavitation, acoustic oscillations, sound of raindrops underwater, Rayleigh-Plesset equation, snapping shrimp, lithotripsy, ultrasonic cleaning, sonochemistry, sonoluminescence, medical reperfusion imaging, and micro-bubble therapy
* [http://natgeochannel.co.uk/podcasts/?id_p=272250478 Extra large bubbles]
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