Final answer:
The spectral transmittivity T of a material can be sketched by understanding that T = 1 - α - p, with α being the spectral absorptivity and p being the spectral reflectivity. Transmissivity represents the portion of incident light that is not absorbed or reflected by the material.
Step-by-step explanation:
To sketch the spectral transmittivity for a spectrally selective diffuse material, when you have the spectral absorptivity (α) and spectral reflectivity (p), you would use the principle that at any given wavelength, the sum of absorptivity, reflectivity, and transmissivity equals unity. This relationship is because all the light incident upon a material is either absorbed, reflected, or transmitted. Therefore, you can calculate the transmissivity (T) as T = 1 - α - p.
Since the absorption spectrum can be represented as a series or pattern of dark lines on a continuous spectrum, and the reflective spectrum describes the wavelength range that is reflected by the material, knowing the spectral absorptivity and reflectivity directly informs us about the transmissive character of the material.
The intensity reflection coefficient α is the ratio of the intensity of the reflected wave to the intensity of the incident (transmitted) wave and is used to derive the aforementioned transmissivity.