Transmission visible light transmittance

For an opaque surface, transmittance t is zero. This reduces Eq. (24.2) to a + p = 1, and thus we only need to determine p. While this assumption is often valid and simplifies things greatly, there are pigments with nonzero transmission. An example in the visible region would be cobalt blues. In the infrared region we cannot rely on our eyes it is possible for a pigment to be partially transparent even if it is opaque in visible light. 

ECTFE has good transmission over a wide range of light frequencies. Its index of refraction is 1.4476 at a wavelength of 589 nm. Figures 3.114 and 3.115 show the transmittance of an ECTFE film in the ultraviolet range and ultraviolet plus visible range, respectively. 

Transmission. The transmittance of glasses is limited by electronic excitiations and light scattering in the UV, by vibronic excitations in the IR, and by reflections and impurity absorptions within the transmission window (in the visible part of the spectmm) Fig. 3.4-27. The UV absorption edge is temperature dependent. An example is shown in Fig. 3.4-28. 

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