In Visible Emissions Smoke School -What is opacity?

Whitlow Smoke School Nation

According to Wikipedia Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc. An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general some may be reflected, some absorbed, some scattered, and the rest transmitted (also see refraction). Reflection can be diffuse, for example light reflecting off a white wall, or specular, for example light reflecting off a mirror. An opaque substance transmits very little light, and therefore reflects, scatters, or absorbs most of it. Both mirrors and carbon black are opaque. Opacity depends on the frequency of the light being considered. For instance, some kinds of glass, while transparent in the visual range, are largely opaque to ultraviolet light. More extreme frequency-dependence is visible in the absorption lines of cold gases. Opacity can be quantified in many ways; for example, see the article mathematical descriptions of opacity. Read more of Wikipedia definitin

Whitlow common sense explanation: Opacity is the term used to refer to the blockage of light. In the old days I had a Kodak SLR 35 mm camera with an aperture that could reduce the amount of light going through the lens.

In visible emissions opacity refers to the amount of sunlight blocked by smoke or dust between the observers eyeball and the contrasting background on the opposite side of the plume.

In the old days the Ringelmann Chart was used to evaluate the density of a smoke plume. The chart was fool proof and fool hardy. The problem was that it only worked on black smoke.

When the government became concerned about white smoke and dust, they switched to the opacity theory. The opacity theory is based on the Ringelmann chart and 20% opacity is equal to number one on the Ringelmann chart.

This is my common man with a common van view of opacity. Opacity is when something gets in the way when you are trying to view something. For example you are trying to view the background- most cases a clear blue sky. In our smoke schools we often use green trees for a background because they give a contrasting background color on cloudy days. I have been trying 30 years to get our customers to plant giant 500 foot trees on top of a building near a smokestack. They just don't listen.

In common terms the smoke or dust gets in the way between you and the background. The smoke or dust reduces the visibility of the background. When you read the opacity focus on the background and not the smoke or dust.

Foot Note: I should note that this is my old definition before the Saints finally beat Brett Favre and won the Super bowl.

My example of opacity. I am in my recliner relaxed, drinking a JAX Beer,

feet propped up. I am eating on a grape, a raisin, a pomegranate, a moon pie, Doritos, cheese dip, cheese grits, and an anchovy pizza. Singing Does your chewing gum loose its flavor on the bedpost every night.

The Saints are playing the Packers. It is the 4th quarter, the 2 minute warning. The Saints are winning by 2 touchdowns. Brett Favre is taking the snap from the center.

The wife Angie stands between me and the TV set hovering with the vacuum cleaner at 99 decibels. She vacuums between me and the TV, now that is 100% opacity, a complete blackout, and 100% frustration.

That ain't all. The Saints are winning by 2 touchdowns at the 2-minute warning. They will manage to somehow snatch defeat out of the arms of victory by letting Brett Favre score 3 touchdowns in 2 minutes. That is why some of us call them the Aints.