Radiation transmitted

Determining Concentration by Turbidimetry In turbidimetry the measured transmittance, T, is the ratio of the transmitted intensity of the source radiation, fy, to the intensity of source radiation transmitted by a blank, Iq. 

In the this form the Beer-Lambert law shows that the intensity of radiation transmitted by an absorbing sample declines exponentially as the length over which the absorption takes place increases. If the radiation, travelling with the speed of light c, takes time tg to traverse the absorbing path f Equation (9.29) becomes ... 

This interaction leads to at least four (4) components, namely R- the radiation reflected, A- the radiation absoit>ed, T- the radiation transmitted, and S - the radiation scattered. A depiction of these interactions is given in the following diagram ... 

Let us assume that the electrolyte is illuminated through the semiconductor electrode as shown in Fig. 5.58 (this is, in principle, possible since the semiconductor is transparent for wavelengths k>hc/eg at which the sensitizer absorbs the radiation). The relative intensity of radiation transmitted to the distance <5D is given by the Lambert-Beer law ... 

Optical background, n - the spectrum of radiation incident on a sample under test, typically obtained by measuring the radiation transmitted through or reflected from the spectrophotometer when no sample is present, or when an optically thin or non-absorbing standard material is present. 

Alaluf M., Dror J., Dahan R. and Croitoru N., Plastic hollow fibers as a selective infrared radiation transmitting medium, J. Appl. Phys., 1992 72 (9) 3878-3883. 

The value of s (the absorbance of a 1 M solution in a 1 cm cell) depends upon the nature of the absorbing species and on the wavelength of the incident radiation. Absorbance is thus seen to be directly proportional both to the concentration of the absorbing species and to the thickness of the absorbing medium. It is related to transmittance T defined as I/I0 (the fraction of radiation transmitted) by the equation... 

For this reason the radiation transmitted by a blank sample is measured and taken to be the effective incident radiation. This blank should be identical to the test sample in all aspects except the presence of the test substance ... 

It is possible to assess the proportion of stray light by measuring the amount of radiation transmitted by samples that are optically opaque at the wavelength to be assessed but that transmit radiation of other wavelengths. The instrument is set to zero and 100% transmittance in the normal way and the opaque substance introduced into the sample compartment. The amount of light transmitted by the sample, measured in percentage transmittance, is... 

Bandwidth refers to the rang> of wavelengths of radiation transmitted by a monochromator and is measured at half maximum transmittance. 

Filters obviously do not provide monochromatic radiation and in many cases the bandwidth may be as great as 100-150 nm (Figure 2.19). Increasing the concentration of the dye may reduce the bandwidth to some extent but will also reduce the amount of radiation transmitted and this then will impose a strain on the detecting system and the sensitivity of the instrument. 

Interference filters modify the intensity of the radiation transmitted by the filter, enhancing the required wavelength and suppressing the unwanted wavelengths. 

This means that if a fixed slit width is used, the radiation transmitted will have different bandwidths depending upon the region of the spectrum. The mechanical efficiency of the mobile slit is therefore extremely important in the ability to select specific wavelengths. 

Figure 2.23 Diffraction gratings. Each line in a grating acts as a separate source of radiation (a) but radiation transmitted at any angle 6 is retarded relative to radiation from the preceding line (b) by the distance x. In the transmitted radiation some wavelengths will undergo constructive interference while the majority will suffer destructive effects. Reflectance gratings (c) are frequently used and the principles of monochro-mation are the same as for transmission gratings.

Optical fiber detectors (OFD) are devices that measure electromagnetic radiation transmitted through optical fibers to produce a quantitative signal in response to the chemical or biochemical recognition of a specific analyte. Ideally, an OFD should produce a specific and accurate measurement, continuously and reversibly, of the presence of a particular molecular species in a given sample medium. Additionally, OFD should pro vide maximum sensitivity and minimal interferences fromsuperfluous ions or molecules to obtain low detection limits. Other attractive features include the miniaturization of the fiber s tip to accommodate single-cell analysis and portable instrumentation to allow in situ analysis. 

Absorption, emission, and Infrared radiation Transmitted infrared radiation... 

Molecular absorption spectroscopy deals with measurement of the ultraviolet-visible spectrum of electromagnetic radiation transmitted or reflected by a sample as a function of the wavelength. Ordinarily, the intensity of the energy transmitted is compared to that transmitted by some other system that serves as a standard. 

Sensor Performance. The intensity of electromagnetic radiation transmitted through an optical path of length L of an atmosphere that is not optically thick can be described by ... 

Figure 6. The intensity of radiation transmitted through the same amount of material is different for uniform versus nonuniform thickness.

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