Transmittance densities

Measurement of optical density of colored image. Macbeth densitometer was used for measurement of transmittance density. 

The transmittance densities of the colored image were measured on polyester film after UV irradiation or after irradiation and washing out in 2% aqueous solution of sodium phosphate. 

The mathematical relationship of incident and reflected light is complicated by such phenomena as diffuse reflectance, ordinary transmittance, and specular reflectance of hemispherically distributed incident light. Based on tin analogy to transmittance density in wet chemistry methods, a mathematical relationship that takes into account all such phenomena is as follows ... 

The sonic tool measures the time taken for a sound wave to pass through the formation. Sound waves travel in high density (i.e. low porosity) formation faster than in low density (high porosity) formation. The porosity can be determined by measuring the transit time for the sound wave to travel between a transmitter and receiver, provided the rock matrix and fluid are known. 

The term electrochromism was apparently coined to describe absorption line shifts induced in dyes by strong electric fields (1). This definition of electrocbromism does not, however, fit within the modem sense of the word. Electrochromism is a reversible and visible change in transmittance and/or reflectance that is associated with an electrochemicaHy induced oxidation—reduction reaction. This optical change is effected by a small electric current at low d-c potential. The potential is usually on the order of 1 V, and the electrochromic material sometimes exhibits good open-circuit memory. Unlike the well-known electrolytic coloration in alkaU haUde crystals, the electrochromic optical density change is often appreciable at ordinary temperatures. 

The original Ringelmann chart was a reflectance chart the observer viewed light reflected from the chart. More recently, light transmittance charts have been developed for both black (1) and white (2) gradations of optical density which correlate with the Ringelmarm chart scale. It is now common practice in the United States to send air pollution inspectors to a "smoke school" where they are trained and certified as being able to read the density of black and white plumes with an accuracy that is acceptable for court testimony. 

The ratio /,//0 is the fraction of the incident light transmitted by a thickness / of the medium and is termed the transmittance T. Its reciprocal /0//, is the opacity, and the absorbance A of the medium (formerly called the optical density... 

Dead time A very short delay introduced before the start of acquisition that allows the transmitter gate to close and the receiver gate to open. Density matrix A description of the state of nuclei in quantum mechanical terms. 

Many early studies of transmitter release depended on measuring its concentration in the effluent of a stimulated, perfused nerve/end-organ preparation. This technique is still widely used to study drug-induced changes in noradrenaline release from sympathetic neurons and the adrenal medulla. However, it is important to realise that the concentration of transmitter will represent only that proportion of transmitter which escapes into the perfusate ( overflow ) (Fig. 4.2). Monoamines, for instance, are rapidly sequestered by uptake into neuronal and non-neuronal tissue whereas other transmitters, such as acetylcholine, are metabolised extensively within the synapse. Because of these local clearance mechanisms, the amount of transmitter which overflows into the perfusate will depend not only on the frequency of nerve stimulation (i.e. release rate) but also on the dimensions of the synaptic cleft and the density of innervation. 

Spectrophotometric measurement at 555 rn.fi of the optical density or per cent transmittance of the resulting color. 

Surprisingly, transparency to the laser light was observed in a 0.5 im thick plasma slab (much thicker than the skin depth) obtained by ultra-fast ionization of a plastic foil at a density orders of magnitude higher than nc [4]. The effect was observed at laser intensities corresponding to ao 1. Figure 8.1 shows the measurements of plasma transmittivity in that experiment vs. the intensity on target of a focused Ti Sa laser pulse (30 fs, 800 nm). 

The transmittance T is a useful measure of how many photons are absorbed nevertheless, most spectroscopists prefer to work in terms of the absorbance A. (Absorbance is also called optical absorbance and optical density - each of these three terms means the same thing.)... 

Classical pulse radar emits high power (Pr) short electromagnetic pulses using a directional transmitting antenna of gain Gt The power density at the target at distance R from the transmitter is equal to [44]... 

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