# Pulp & Paper Questions and Answers – Kubelka-Munk Theory

This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Kubelka-Munk Theory”.

1. The crucial optical properties include reflectance colour and brightness, especially diffuse reflectance and opacity.
a) True
b) False

Explanation: The optical properties of paper are extremely crucial for many of its utilizes, especially when paper is utilized for printing. Most crucial ones are reflectance colour and brightness, especially diffuse reflectance and opacity.

2. A normalized approach to the optical properties of paper allows one to predict the properties of paper to avoid a labour intensive trial—and—error work approach.
a) True
b) False

Explanation: Optical projection tomography (O.P.T.) is a recently introduced 3-dimensional imaging technique for primary utilize the developmental biology and gene expression studies.

3. Paper with 85.0% reflectance relative to a certain MgO standard that is known to have an absolute reflectance of 0.980 corresponds to an absolute reflectance of ___________
a) 0.833
b) 1.25
c) 6.35
d) 0.687

Explanation: Absolute reference is calculated as 0.850 x 0.980 = 0.833

4. ___________ is the property of a material that indicates the ability to hide what is behind it.
a) Transparency
b) Opacity
c) Glossiness
d) Reflectivity

Explanation: Opacity is the calculation of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it tells about the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc.

5. The reflectance of an (effectively infinite) thick pad of paper is R1 and is known as ___________
a) Transparency
b) Opacity
c) Glossiness
d) Reflectivety

Explanation: It is the fraction of incident electromagnetic power that’s reflected at an interface. The reflectance of a single sheet with a perfectly white backing is given as R1 and the corresponding opacity is called the ideal opacity.
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6. If one knows the ___________ and reflectivity of a paper, the changes in these properties with a change could be predicted.
a) Weight ratio
b) Contrast ratio
c) Curtis ratio
d) Kraft ratio

Explanation: It’s the ratio of the luminance of the brightest color to that of the darkest color that the system is capable of giving out. A high contrast ratio’s a required aspect of any display.

7. The Kubelka—Munk theory of light allows one to predict quantitatively the behaviour of light in coatings such as ___________ for which it was developed; this work has become the basis of much of this field.
a) Thinner
b) Paper
c) Paint
d) Plastic

Explanation: Kubelka—Munk theory is utilized in papermaking in many ways. If one knows the optical properties of each pulp, filler, and dye utilized in papermaking, then the optical properties of a paper made with any combination of the materials could be predicted. If one knows the contrast ratio and reflectivety of a paper, the changes in these properties with a change in basis weight could be predicted.

8. The Kubelka—Munk theory was developed to define properties based on the thickness of a material (X), but in the case of porous materials like ___________ workers quickly started utilizing basis weight.
a) Thinner
b) Paper
c) Paint
d) Plastic

Explanation: It isn’t terribly good for dyed papers when light absorption reaches a greater level. A limiting assumption is that the particles making up the layer must be much less than the total thickness.

9. _____________ filters could be utilized to remove the effect of gloss light reflected according to Fresnel’s law which has a degree of polarization.
a) Polarized
b) Doped
c) Magnified
d) Electrocuted

Explanation: The ability of waves to oscillate in more than a single direction; in particular polarization of light, responsible for example for the glare-reducing effect of polarized sunglasses.

10. What is the name of the equation?

Sp = (S-(1-y)Sf) / (y)

a) Steele
b) Kraft
c) Michaud
d) Tomas

Explanation: Steele in 1937 gave the calculation to determine the scattering coefficient of the pigment filler in the filled paper as a function of the scattering power of the fiber, the scattering coefficient of the filled paper (5), and the fraction of filler in the filled sheet (y).

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