UGC NTA NET/JRF Exam, Environmental Sciences, June-2020

Total Questions: 100

81. Given below are two statements: One is labelled as Assertion (A) and other is labelled as Reason (R).

Assertion (A) : Isomorphous substitution is the source of constant charges on soil silicate clays.

Reason (R) : Cations of comparable size substitute each other in respective tetrahedral and octahedral sheets in silicate clays.

In light of the above statements, choose the correct answer from the options given below:

Correct Answer: A. Both (A) and (R) are true and (R) is the correct explanation of (A)
Solution:

The wide variability in the electrochemical properties of silicate clays is due to the common process of isomorphous substitution. In this process, cations of comparable size substitute for Si, Ah and Mg ions in the respective tetrahedral and octahedral sheets.

For example, the atomic radius of Al is only slightly larger than that of Si, and Al can therefore fit in the center of the tetrahedron to substitute for Si, Ions such as Fe and Zn can substitute for Al or Mg in the octahedral sheet due to their similar size.

Isomorphous substitution can occur in either or both of the tetrahedral or octahedral sheets. Because of numerous ionic substitutions, silicate clays in soil are described by structural or unit layer formulae rather than simple chemical formulae.

82. Yaw control used in wind turbine generator is a:

Correct Answer: B. The mechanism to keep the rotor axis along wind direction.
Solution:

All horizontal axis wind turbines use forced yawing, i.e. they use a mechanism which uses electric motors and gearboxes to keep the turbine yawed against the wind.

83. Given below are two statements: One is labelled as Assertion (A) and other is labelled as Reason (R).

Assertion (A) : Some countries are immune to the impacts of climate change.

Reason (R) : The net contribution of some countries is less than 1% towards the global CO₂ emissions as a whole.

In light of the above statements, choose the correct answer from the options given below:

Correct Answer: D. (A) is false, but (R) is true
Solution:

The net contribution of some countries is less than 1% towards the global CO₂  emissions as a whole.

84. Given below are two statements: One is labelled as Assertion (A) and other is labelled as Reason (R).

Assertion (A) : Solar and wind energy systems require quite large structures relative to power produced.

Reason (R) : Energy flux densities associated with solar energy and wind energy are on average small.

In light of the above statements, choose the most appropriate answer from the options given below:

Correct Answer: A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Solution:

Low energy flux density and large sunshine fluctuation are the fundamental characteristics of solar radiation, and they are also an insuperable barrier for humans in the largescale exploitation and utilization of solar energy.

In solar thermal plants, concrete, metals and glass are the most important materials for which, as with components of conventional thermal power stations, no significant environmental problems are foreseen.

85. Given below are two statements: One is labelled as Assertion (A) and other is labelled as Reason (R).

Assertion (A) : Hydrofluorocarbons (HFCs) and hydrochlorofluorocarbon (HCFCs) are used as substitute compounds for chlorofluorocarbons (CFCs).

Reason (R) : HCFCs and HFCs are quite susceptible to reaction with OH radicals in the troposphere.

In light of the above statements, choose the correct answer from the options given below:

Correct Answer: A. Both (A) and (R) are true and (R) is the correct explanation of (A)
Solution:

Two of the chemical classes under consideration for replacing CFCs are hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). HCFCs contribute to the destruction of stratospheric ozone, but to a much lesser extent than CFCs.

HFCs and HCFCs are susceptible to attack by OH radicals in the troposphere (lower atmosphere). HFCs do not contain CI atoms and so do not have any ozone depletion potential associated with the well established chlorine catalytic cycle. Hence, Both (A) and (R) are true and (R) is the correct explanation of (A).

86. Given below are two statements: One is labelled as Assertion (A) and other is labelled as Reason (R).

Assertion (A) : Regression analysis is suitable for two variables having a linear causal relationship between them.

Reason (R) : The causal relationship between two variables is never curvilinear.

In light of the above statements, choose the most appropriate answer from the options given below:

Correct Answer: C. (A) is correct, but (R) is not correct
Solution:

Regression analysis is suitable for two variables having a linear causal relationship between them.

A curvilinear relationship is a type of relationship between two variables that has a pattern of correspondence or association between the two variables that change as the values of the variables change.
Hence, (A) is correct, but (R) is not correct.

87. Given below are two statements.

Statement I : Leslie's matrix population model is a discrete and ageindependent model.
Statement II : The first row in Leslie's projection matrix represents fertility.

In light of the above statements, choose the most appropriate answer from the options given below:

Correct Answer: D. Statement I is incorrect, but Statement II is correct
Solution:

Age-classified models place estimates of fertility and survival rates in a square "projection matrix". In the simplest case (Leslie matrix) the top row of the projection matrix represents age-specific fertility, while the subdiagonal represents age-specific survival.

A common extension is to add an element at the lower right that represents survival of 'adults'. The remaining elements of the projection matrix are zero.

88. Arrange the environmental movements in chronological order.

(a) Silent Valley struggle
(b) Chipko movement
(c) Appiko movement
(d) Narmada Bachao movement
Choose the correct answer from the options given below:

Correct Answer: B. (b), (a), (c), (d)
Solution:

The Chipko movement or Chipko Andolan, was a forest conservation movement in India. It began in 1973 in Uttarakhand, then a part of Uttar Pradesh (at the foothills of Himalayas) and went on to become a rallying point for many future environmental movements all over the world.

Silent Valley struggle was started in 1973 by an NGO led by school teachers and the Kerala Sastra Sahithya Parishad(KSSP) to save the Silent Valley from being flooded by a hydroelectric project.

The valley was declared as Silent Valley National Park in 1980. The Appiko Movement, a movement similar to the Chipko Movement, was launched in September 1983 by the representatives of a Yuvak Mandali to save the Western Ghats in Southwest India.

It was observed by the representatives of the Yuvak Mandali that in areas, which were easily accessible, there was an excessive concentration of trees reserved for felling, and there was also excessive damage to other trees during such course of felling.

Narmada Bachao Andolan is the most powerful mass movement, started in 1985, against the construction of huge dam on the Narmada river.

Narmada is the India's largest west flowing river, which supports a large variety of people with distinguished culture and tradition ranging from the indigenous (tribal) people inhabited in the jungles here to the large number of rural population.

89. Regarding Bharat Stage (BS-VI) vehicular emissions norms, choose the correct statements:

(a) BS (VI) emission norms are equivalent to Euro (VI) norms.
(b) BS (VI) norms require the up-gradation of engine and emission control technology
(c) BS(VI) norms are applicable to all categories of the vehicles including two, three and four-wheelers.
(d) BS (VI) norms do not require any change in fuel quality.
Choose the correct answer from the options given below:

Correct Answer: A. (a), (b), (c) only
Solution:

On February 19, 2016, the Indian Ministry of Road Transport and Highways (MoRTH) issued a draft notification of Bharat Stage (BS) VI emission standards for all major on-road vehicle categories in India.

BS VI proposal include enhanced OBD requirements for all vehicle classes, with firstever OBD specifications for two- and threewheeled vehicles, and the introduction of emission limits on nitrogen oxides (NOX).

Carbon monoxide (CO), and hydrocarbon (HC) for two-wheelers that are equivalent to proposed BS VI norms for light-duty gasoline passenger vehicles. Indian regulations for four-wheeled vehicles follow European Union regulatory pathways.

90. Which among the following atmospheric constituents have a negative radiative forcing?

(a) Tropospheric ozone
(b) Stratospheric ozone
(c) Sulphate Aerosol
(d) Nitrous oxide
Choose the correct answer from the options given below.

Correct Answer: B. (b) and (c) only
Solution:

The radiative forcing due to tropospheric ozone and sulfate aerosol changes is evaluated using a radiative wideband model. Stratospheric ozone and Sulphate Aerosol have a negative radiative forcing.