What is the reflectance of an object?
The term reflectance is defined as the ratio of reflected radiant flux (optical power) to the incident flux at a reflecting object – for example, an optical component or system. It generally depends on the direction of incident light and on the optical frequency or wavelength.
What is an object’s surface spectral reflectance?
Spectral reflectance is the ratio of reflected energy to incident radiation (ɸr/ɸ) as a function of the wavelength. The spectral reflectance characteristics of most targets depend upon the illuminating region of the EM spectrum.
What does a reflectance spectral curve tell us?
Spectral reflectance curves are used to determine paper color, brightness, and whiteness, important optical properties that dramatically affect the quality of material printed on the paper surface. See Color, Brightness, and Whiteness.
How do objects have a signature of reflectance?
Spectral reflectance signatures result from the presence or absence, as well as the position and shape of specific absorption features, of the surface.
What is the reflectance of glass?
The light passing through glass is not only reflected on the front surface, but also on the back. In fact, the light may be reflected back and forth several times. Therefore, the total reflectance through a glass window is 2·R / (1+R).
Why do metals have high reflectivity?
In the case of metals, these electrons are only loosely attached to the metal atoms, so they can move around (which is related to the fact that metals conduct electricity). When light hits the metal, the electrons interact with the light and cause it to reflect.
Why is spectral reflectance important?
Spectral Reflectance Properties The most important surface features are colour, structure and surface texture. These differences make it possible to identify different earth surface features or materials by analysing their spectral reflectance patterns or spectral signatures.
Why is the spectral reflectance curve necessary?
The reflectance characteristics of the surface features are represented using these curves. These curves give an insight into the spectral characteristics of different objects, hence used in the selection of a particular wavelength band for remote sensing data acquisition.
What is spectral signature of an object?
Spectral signature is the variation of reflectance or emittance of a material with respect to wavelengths (i.e., reflectance/emittance as a function of wavelength). The spectral signature of stars indicates the composition of the stellar atmosphere.
What influences spectral reflectance?
The spectral reflectance curve of bare soil is considerably less variable. The reflectance curve is affected by moisture content, soil texture, surface roughness, presence of iron oxide and organic matter. These factors are less dominant than the absorbance features observed in vegetation reflectance spectra.
What is the reflectivity of water?
Water reflectance Reflectance of smooth water at 20 °C (refractive index 1.333).
What is the reflectance of windows?
Does plastic reflect light?
Rough plastic scatters light that strikes it in all directions. Some light is sent toward your eye. Smooth plastic reflects light that strikes at a grazing angle back inside. Since the light is reflected back inside, you don’t see light there.
Does wood reflect light?
Wood, concrete and paper don’t reflect, partly because their surfaces are not very smooth, and he light that hits the surface of these materials is scattered all over.
How do you calculate reflectance of a material?
Reflectivity can be calculated as p(y) = Gr(y)/Gi(y) where p is the reflectivity, y is the wavelength of the light, Gr is the reflected radiation and Gi is the incident radiation. Calculate reflectance from the reflectivity. Reflectance is the square of the reflectivity so q(y) = (Gr(y)/Gi(y))^2.
What is spectral reflectance?
Spectral Reflectance is the measure of the wavelength of the electromagnetic energy reflected from a surface in a given waveband to the energy incident in that waveband.
What is a spectral reflectance?
3.2. The spectral reflectance is the reflectance measured at a given Ts and λ, within a small wavelength interval, Δλ, centered at λ [7]. Spectral reflectance is typically named monochromatic reflectance and may be specular, diffuse, or hemispherical.
What are the factors affecting the spectral image?
The five external factors considered are: size of the viewed area, orientation and inclination of the view axis, sun elevation, nebulosity and wind speed.
What types of waves can humans see?
The visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view. More simply, this range of wavelengths is called visible light. Typically, the human eye can detect wavelengths from 380 to 700 nanometers.
How do you calculate the spectral reflectance of an object?
The spectral reflectance of the object at every wavelength is then b 1 r 1 (λ) + b 2 r 2 (λ) + b 3 r 3 (λ). This, too, is a fairly reasonable assumption because most spectral reflectances found in natural scenes can be described moderately well by a weighted sum of three components ( Cohen, 1964 ).
What is reflectance used for in vegetation spectral analysis?
For vegetation spectral analysis, this type of reflectance has been used either as a method to standardize spectral libraries obtained at different measurement setups or to potentially improve the spectral discrimination.
Is the spectral reflectance affected by quantitative manipulations of the measured reflectance?
In case no quantitative manipulations of the measured spectral reflectance have been performed, the spectral reflectance is unaltered.
What are the factors that affect the spectral reflectance?
Furthermore, at certain wavelength, the spectral reflectance are influenced by the vegetation structure, soil and vegetation moisture, the texture and external factor like sensor geometry.