The movement of particles from an area of high concentration to an area of low concentration.

Film Term:
  1. A filter used on the camera to create a soft focus effect.
  2. A white or pearlecent sheet of material used on a movie light to soften the shadows.

Glossary of Film Terms -
reprinted with permission

A cryptographic technique that seeks to obscure the statistical structure of the plaintext by spreading out the influence of of each individual plaintex digit over many ciphertext digits.

Geographically speaking, the spread of ideas or knowledge (innovation) from their origins to areas where they can be adopted. Also known as cultural diffusion.

Three Forces working against diffusion:
Distance. The farther from it's source the less likely an innovation will be adopted.
Time. The acceptance of an innovation becomes less likely the longer it takes to reach potential adopters.
Cultural Barriers - Ideas may not be adopted because of prevailing attitudes or taboos.

Diffusion in this sense is becoming more and more obsolete. The reason? Technology. How easy is it to get your idea to people on the other side of the world? Quite easy...just look at Everything2...

More on diffusion..

As Elm Tree points out, diffusion is: 'The movement of particles from an area of high concentration to an area of low concentration.'

Diffusion is a vital process for life. It keeps every cell in your body alive by allowing cells to get nutrients from and lose wastes to surrounding fluid. It makes your muscles work. It makes the air around you breathable. It makes your hands puffy if you stay in the bath for too long etc. Basically, no diffusion, no life.

So, how does diffusion work? Everything you see around you is made of molecules and atoms. These particles have kinetic energy (ie, they bounce around randomly). This means that over time, you get a homogeneous spread of particles around their container. From the outside, it looks like particles are moving from an area of high concentration to an area of low concentration though in fact, particles are moving in all directions randomly all the time.

Diffusion can occur across membranes. A specialised form of diffusion is called osmosis.

Diffusion is, simply speaking, the spread of particles from a lower concentration to a higher one. Diffusion takes place in both gases and liquids, and is especially noticeable if you put two different coloured liquids together in a glass. Due to the random motion of the particles, the two colours will mix into each other until the mixture is uniform. The connection between concentration of the diffusing substance and its rate of diffusion was first formulated by Adolf Fick.

J = DA(C1-C2)/Δx

where J is the mass movement per second, Δx is the length of the medium the substance is diffusing through (we are assuming a cylindrical container) and C1 and C2 are, of course, the concentrations of the two substances. J is measured in mass over seconds or moles per second, depending on the unit used to describe concentration.

Dif*fu"sion (?), n. [L. diffusio: cf. F. diffusion.]


The act of diffusing, or the state of being diffused; a spreading; extension; dissemination; circulation; dispersion.

A diffusion of knowledge which has undermined superstition. Burke.

2. Physiol.

The act of passing by osmosis through animal membranes, as in the distribution of poisons, gases, etc., through the body. Unlike absorption, diffusion may go on after death, that is, after the blood ceases to circulate.

Syn. -- Extension; spread; propagation; circulation; expansion; dispersion.


© Webster 1913.

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