Lambert cosine-law

Lambert-Beer law, 24 89. See also Beer-Lambert expression Lambert cosine law, 23 121 Lambs... 

Figure 30.4 also shows the radiation level in Tulsa for an object positioned horizontal to the earth s surface. For this case, the radiation varies much more dramatically from about 150 to 290 Btu/hr-fh (473 to 915 W/m ) throughout the year. Peak radiation levels occur during the summer months mainly because the view allows more solar radiation to strike an area positioned horizontal to the earth. The amount of radiation that strikes an area positioned horizontal to the earth can be described by the Lambert cosine law ... 

Flare gas flow rate and composition, wind speed and direction, the location of the flare flame s epicenter can vary during a flare test. Due to the Lambert cosine law, the maximum radiation reading will be measured when the radiometer is aimed directly at the flare epicenfer. If is often difficult to predict the location of fhe epicenfer and to position the radiometer to aim at the epicenter prior to a flare fesf. 

The Lambert cosine-law has to be valid (isotropic distribution of stray light), that means the regular reflectance can be neglected. 

Perfect diffuser n. Theoretical ideal white substance which reflects 100% of the incident light in a perfectly diffuse way official CIE reference white to which colors being measured are compared a Lambert surface, following the Lambert cosine law perfectly. 

Fig. 5. The angular distribution of reflected Kght on a matte surface foDowing the Lambert cosine law the terms used in the Lambert law are illustrated.

Fig. 6. The angular reflected energy distribution for the Lambert cosine law versus the Seeliger diffuse reflectance law.

Lambert s cosine law Lambic beer Lamb modes Lambs Lamb wave Lamellae Lamepon Laminar flow Laminated fabrics Laminated glass... 

The intensities of diffuse reflectance and fluorescence are both distributed over the solid angle according to Lambert s cosine-law. An ultraviolet-visible (UV/VIS)-... 

The radiance observed from a body depends on the elevation angle 0, which is the angle from the surface normal at which the measurement is made. If 8 is independent of 0, the radiance at 6, is given by Lambert s cosine law ... 

Since the observer views radiation from all parts of the extended area A, but at different angles a, Lambert s cosine law, which states that the intensity in a given direction will change in proportion to the cosine of the angle from the normal, has to be taken into account.) Equ. (10.45a) is equivalent to... 

In radiative exchange calculations, it is preferable to use the model, described in the previous section, of a grey, diffuse radiating body as a simple approximation for the radiative behaviour of real bodies. As Lambert s cosine law is valid for this model, we denote these bodies as grey Lambert radiators. The energy radiated from them is distributed like that from a black body over the directions in... 

The blackbody spectral and total intensities are independent of direction so that emission of energy into a direction at 6 away from the surface normal direction is proportional to cos 6. This is known as Lambert s cosine law. 

Two main types of models for tubular lamps (the most widely used) will be described. There are lamps that produce an arc that emits radiation and, consequently, photons come out directly from such an arc. Emission is made by the whole lamp volume. We call this process Voluminal Emission. There are other types of lamps in which the discharged arc between electrodes induces an emission produced by some particular substance that has been coated on the lamp surface. We call this process Superficial Emission. Voluminal emission may be safely modeled as an isotropic emission in this case the specific intensity associated with each bundle of radiation originated in some element of volume of the lamp is independent of direction, and the associated emitted energy (per unit time and unit area) is also isotropic (Figure 6.6). On the other hand, it seems that superficial emission can be better modeled by a diffuse type of emission that is also known as one that follows the Lambert s cosine law of emission in this case the emitted intensity is independent of direction but the emitted energy depends on the surface orientation and follows the cosine law equation (Figure 6.7). The following assumptions are made (Irazoqui etal., 1973) ... 

The extinction coefficient depends on temperature, pressure, composition, and the wavelength of the incident radiation. It may be pointed out that Equation 19.9 is also termed as Lambert s law or Bougher-Lambert law, and Beer s law when the extinction coefficient is put in mass terms, but it must not be confused with Lambert s cosine law. 

Lambert s law of reflection The flux reflected per unit solid angle is proportional to the cosine of the angle measured from the normal (perpendicular) to the surface. If the reflected flux is isotropic, the surface is said to be a perfect Lambertian reflector or a perfect diffuser. 

Scattering is the opposite effect of regular reflection. If the surface is inhomogeneous by some micrometers within the irradiated area, one finds diffuse reflection [9]. Each area forms a center of reflection and the different reflected beams superimpose to result interference. The form of this intensity distribution within space can be described according to Lambert s cosine law. This effect is used in thin-layer chromatography [9,11]. 

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