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

Total Questions: 100

1. Good absorbers are good emitters. This statement refers to which of the following laws?

Correct Answer: D. Kirchhoff's Law
Solution:

According to Kirchhoff's law, a = e, or the absorptivity of a body equals its emissivity. A good absorber is a good emitter.

As a good absorber is poor reflector, emitting (or radiating) ability of body is oppositely related to its ability to reflect. Therefore, good emitter (or radiator) is a poor reflector.

2. A sample of air has a relative humidity of 60%. Given that the Saturated Vapour Pressure of water is 2260 Pa, calculate the vapour pressure of the air at 20°C.

Correct Answer: D. ~1356 Pa
Solution:

3. Which among the following is short-lived species in the atmosphere?

Correct Answer: D. OH radical
Solution:

Upon interaction with water and oxygen moieties, CAPs generate hydroxyl radicals •OH and superoxide radical anions O₂•⁻. These short-lived species possess highly oxidising and cytotoxic properties, and are suggested to be one of the main causes of biomedical activity of cold plasma.

4. The chemical composition of CFC-113 is:

Correct Answer: A. CF₂ CICFCI₂
Solution:

5. Soil humic acids are:

Correct Answer: B. Insoluble in acid
Solution:

Humic acids are insoluble in water at acid pH, whereas fulvic acids are also derived from humic substances but are soluble in water across the full range of pH.

Humic and fulvic acids are commonly used as a soil supplement in agriculture, and less commonly as a human nutritional supplement.

6. Volatile Organic Compounds (VOCs) are of great concern because:

Correct Answer: C. They contribute to a general increase in reactive hydrocarbons in the atmosphere
Solution:

Volatile organic compounds (VOCs) also referred to as solvents, are chemicals that evaporate easily at room temperature. VOCs are a class of liquid organic chemicals of variable lipophilicity and volatility.

VOCs are classified according to molecular structure or functional group. These include aliphatic hydrocarbons (many of which are chlorinated - halocarbons), aromatic hydrocarbons, alcohols, ethers, esters, aldehydes, etc.

Solvents may be utilized individually or as mixtures containing several ingredients. Most VOCs contribute in varying degrees to the formation of ground levels of ozone.

7. Hyperthermophilic microorganisms prefer temperatures in excess of:

Correct Answer: B. 80°C
Solution:

Hyperthermophiles prefer high temperatures, e.g. above 80°C for optimal growth.

They are able to thrive in such extreme temperatures because they contain enzymes that can function at high temperatures. They are an example of extremophiles.

While they are able to live at high temperatures, most organisms would not be able to survive upon exposure to the same temperature.

8. The most toxic form of mercury in water is:

Correct Answer: В. H₃С - Hg⁺
Solution:

The toxic effects of mercury depend on its chemical form and the route of exposure. Methylmercury [CH₃Hg] is the most toxic form.

It affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste, and sight.

Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults.

9. One Dobson unit, represents the ozone layer of thickness:

Correct Answer: C. One-hundredth of a millimeter
Solution:

Ozone is measured as Dobson units. And a Dobson unit of gas is equal to a layer of gas, with a thickness of one-hundredth of a millimeter at the surface of the Earth.

The ozone in the atmosphere is measured by about 300 Dobsons. Ozone is also known as a trace gas, meaning there are very few amounts in the atmosphere.

10. The transitional zone (ecotone) between freshwater and terrestrial ecosystems is known as:

Correct Answer: A. Riparian Zone
Solution:

Riparian ecosystems are associated with water and occur as transition zones or ecotones between aquatic and terrestrial (upland) ecosystems.

These transition zones have distinct vegetation and soil characteristics. Riparian ecosystems are uniquely characterized by the combination of high species diversity, high species densities, and high productivity.

Continuous interactions occur between riparian, aquatic and adjacent terrestrial ecosystems through exchanges of energy, nutrients, and species.