Difference between reflectance and integrated reflectance
Answers
Answer:
Without reflected light, our eyes would be unable to see the color or texture of objects. Reflection allows us to perceive the world around us. The human eye does amazing things with reflected light, using it to identify shapes and patterns, and even sense the distance of an object. To a spectrometer, however, reflection is simply the fraction of light reflected from a surface as a function of wavelength.
When properly measured, spectral reflectance can yield much of the same information as the eye, but it does so more quantitatively and objectively. A spectral reflectance measurement can compare two yellow objects, or different textures. It can also offer information about the material from which a sample is made, since light that is not reflected from a sample is absorbed due to its chemical composition, otherwise it is scattered or transmitted.
Explanation:
Advantages
Non-destructive: Unless the sample is photo-sensitive, the measurement can be repeated endlessly without altering the sample.
Quantitative: More accurate than the human eye for comparing objects or surfaces.
Local: Only the surface of the sample is measured, not its interior.
Explanation:
For the latter, the spectral distribution of the incident radiation has to be specified. In addition, reflectance, transmittance and absorptance might also depend on polarization and geometric distribution of the incident radiation, which therefore also have to be specified.The reflectance r is defined by the ratio of reflected radiant power to incident radiant power. For a certain area element dA of the reflecting surface, the (differential) incident radiant power is given by the surface's irradiance Ee, multiplied with the size of the surface element, thus
dFe,incident = Ee dA
and the (differential) reflected radiant power is given by the exitance Me, multiplied with the size of the surface element:
dFe,reflected = Me dA
Thus,
or
Me = r Ee
Total reflectance is further subdivided in regular reflectance rr and diffuse reflectance rd, which are given by the ratios of regularly (or specularly) reflected radiant power and diffusely reflected radiant power to incident radiant power. From this definition, it is obvious that
r = rr + rd
The transmittance t of a medium is defined by the ratio of transmitted radiant power to incident radiant power. Total transmittance is further subdivided in regular transmittance tr and diffuse transmittance td, which are given by the ratios of regularly (or directly) transmitted radiant power and diffusely transmitted radiant power to incident radiant power.
Again,
t = tr + td