Intensity of incident light

Relationships between the intensity of incident light, sample thickness, concentration and intensity of transmitted light are embodied in Beer s law and Lambert s law. ... 

Quantitative aspects. The total fluorescence intensity, F, is given by the equation F = Ia(f> where Ia is the intensity of light absorption and 4>f the quantum efficiency of fluorescence. Since 70 = 7a + 7t where 70 = intensity of incident light and 7t = intensity of transmitted light, then... 

Io Intensity of incident light MFT, MI Melt flow index... 

Ts = intensity of scattered light transmitted by the sample Tj = intensity of incident light... 

Aa absorbance at wavelength A Iq intensity of incident light I intensity of transmitted light ex (molar) absorption coefficient at wavelength A c concentration d length of optical path within the cuvette. 

Photoinitiated free radical polymerization is a typical chain reaction. Oster and Nang (8) and Ledwith (9) have described the kinetics and the mechanisms for such photopolymerization reactions. The rate of polymerization depends on the intensity of incident light (/ ), the quantum yield for production of radicals ( ), the molar extinction coefficient of the initiator at the wavelength employed ( ), the initiator concentration [5], and the path length (/) of the light through the sample. Assuming the usual radical termination processes at steady state, the rate of photopolymerization is often approximated by... 

Except for the movable photomultiplier tube, a light scattering photometer is very nearly identical to an ordinary spectrophotometer, which measures the ratio of the intensity of transmitted light to the intensity of incident light /,//0. The absorbance per unit optical path cabs is defined in terms of this quantity as... 

The measurement of quantum yield is a more complicated process. Before these measurements can be made, the instrument must be calibrated. A thermopile or chemical actinometer may be used to measure the absolute intensity of incident light on the sample. Alternatively, quantum yields may be measured relative to some accepted standard. Two commonly used fluorescence standards are quinine sulfate in 0.5 M H2S04 (jQ = 0.70) and fluorescein in 0.1 M NaOH (f9 = 0.93). The quantum yield of the unknown, Q, is then calculated by Equation 5.7. 

A photochromic substance is one that changes colour under the influence of light, this change being reversible in the dark. The photochromic substance should therefore adapt its transmission to the intensity of incident light the stronger the light, the more the photochromic system absorbs it. 

A step common to most optical sensing processes is the absorption of a photon. The quantitative relationship between the concentration of the absorber C and the attenuation of intensity of incident light is known as the Lambert-Beer law. For its derivation, it is convenient to invoke the particulate character of light, which says... 

The simplest geometry to measure fluorescence of transparent samples is instrumentation of excitation at 90°. In this case, it can be considered that the intensity of absorbed light (7abs) is equal to the intensity of incident light (I0) minus the intensity of transmitted light (/,rans).The transmitted light is expressed by Lambert-Beer Law ... 

By Eq. (16.22), one can observe that the intensity of fluorescence for transparent samples is directly proportional to the intensity of incident light in the sample, depending on the absorptivity of the sample in the wavelength of excitation and concentration of chromospheres. Figure 16.34a shows a typical curve for the fluorescence intensity as a function of fluorophore concentration. 

Equation (7.14) describes the relationship that exists between fluorescence intensity at a precise emission wavelength and intensity of incident light (Iq), fluorophore quantum yield, and its optical density at the excitation wavelength. 

I0 = intensity of incident light / = intensity of transmitted light s = molar absorptivity or molar extinction coefficient c = concentration of solute in moles/litre l = cell (path) length (cm)... 

Separation and integration from I0 (intensity of incident light) to I (the intensity of transmitted light) and over the total sample thickness results in the following ... 

Generating vibrant images on paper is one of the primary goals of printing. A parameter used to quantify the darkness of prints is the optical density, OD = — log (7/7o), where lo is the intensity of incident light on a print, and I is the intensity of hght reflected from a print. Alternatively, color coordinates such as L, a, b are also used to quantify color prints, where L is the luminance (lower L darker),... 

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