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

Total Questions: 100

11. Which one of the following silicate clay minerals exhibits highest interlayer expansion?

Correct Answer: A. Montmorillonite
Solution:

Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay.

Similar to many other clays, montmorillonite swells with the addition of water. Montmorillonites expand considerably more than other clays due to water penetrating the interlayer molecular spaces and concomitant adsorption.

The amount of expansion is due largely to the type of exchangeable cation contained in the sample.

12. Beside steam, next gas in order of abundance emitted from a volcanic eruption is:

Correct Answer: C. Carbon dioxide
Solution:

13. Heteromorphic rocks have:

Correct Answer: B. Different mineral composition arising from similar magmas under different conditions of crystallization.
Solution:

The phenomenon of rocks of different mineral composition arising from similar magmas under different conditions of crystallisation is termed heteromorphism by Lacroix, and the products are said to be heteromorphs of each other. Thus leucite-basalt is a heteromorph of mica-syenite, and allivalite of augitite.

14. A rock composed entirely of crystals is said to be:

Correct Answer: C. Holocrystalline
Solution:

Crystallinity is measured by the ratio subsisting between crystallized and non crystallized matter.
Types of Crystallinity
1. Holocrystalline
2. Holohyaline
3. Hemicrystalline/Hypocrystalline/Merocrystalline
Holocrystalline: A rock composed entirely of crystals is said to be Holocrystalline. Holocrystalline texture is characterized by deep-seated or intrusive igneous rocks. Example: Granite, Gabbro, Syenite.

15. A Si-solar cell has the minority carrier saturation current = 60 nAm⁻² and solar radiation-induced current = 600 Am⁻². If the ambient temperature is 27°C, what is the open-circuit voltage of the solar cell?

Correct Answer: A. ~0.6 V

16. Which one among the following Solar Collectors has the highest Concentration Ratio or CR value (a measure of the efficiency of the Solar Collectors)?

Correct Answer: D. Paraboloid dish collector
Solution:

The light concentration process is typically characterized by the concentration ratio (С). By physical meaning, the concentration ratio is the factor by which the incident energy flux (I) is optically enhanced on the receiving surface.

The paraboloid dish solar concentrating system uses a parabolic concentrating dish to focus sunlight on a thermal cavity receiver. The receiver attains high temperature which in turn heats the water or thermal fluid inside the cavity.

The heated fluid then transfer its heat to end industrial applications. The thermal energy attained is in 100 - 400 °C temperature range.

The paraboloid can have a reflector area of up to 90 m². And a system like these can produce more than 50 kW of thermal output at 1000 W/m² solar insolation.

17. The fast neutrons produced in the process of nuclear fission of ²³⁵U, have an average energy of about:

Correct Answer: С. 2.0 Mev

18. A small hydropower station based on the conversion of the kinetic energy of a river water generates power. If the flow of water is 10 m³s⁻¹ and the speed of water is 3 ms⁻¹, what is the maximum power the station can generate? (Assume efficiency of the power station to be 0.6)

Correct Answer: B. 27 kW

19. The maximum cross-section for the fusion reaction ₁²H + ₁³H is reached at energies of nuclei at:

Correct Answer: B. ~100 keV

20. Solve the following question?

Correct Answer: B. 60 and 40, respectively