UGC NTA NET/JRF Exam, Environmental Sciences, March-2023

Mohs scale of mineral hardness is a qualitative ordinal scale that characterizes the scratch resistance of various minerals.

• Calcite has a hardness of 3. It can be easily scratched by a knife or a coin.
• Topaz possesses a hardness of 8. Due to this, topaz is often used in jewelry as it's relatively resistant to scratching.
• Apatite stands at a hardness of 5, which makes it about the average hardness of most minerals.
• Quartz has a hardness of 7. Quartz is a common mineral found in Earth's crust, and due to its hardness, it's often used in making glass and in the electronics industry.

The elemental composition varies in organic substances, but their relative percentage can be broadly categorized as:

• Carbon generally makes up 60-90% of the composition in organic compounds. It's the basic building block of life and the backbone of organic molecules.

• Hydrogen can range between 1-12%. It's abundant in hydrocarbons and other organic molecules.

• Oxygen typically has a composition between 2-20%. It's found in most organic molecules, especially in carbohydrates, lipids, proteins, and nucleic acids.

• Nitrogen has a range of 1-3%. It's an essential element in amino acids, the building blocks of proteins, and in nucleic acids.

Environmental Impact Assessment (EIA) is a tool used to predict the environmental effects of a project:

• Scoping is the process to identify key issues and impacts to establish study limits. It determines the content and extent of the matters that will be assessed during the EIA process.

• Evaluation is the step where the significance and social importance of measured impacts, especially the adverse ones, are determined.

• ES Review involves the systematic appraisal of the quality of the Environmental Impact Statement (EIS) and checks its compliance with legislation. It determines if any modification is required.

• Monitoring ensures compliance with terms and conditions and monitors environmental impacts to ensure they are within accepted limits.

The electromagnetic spectrum comprises various types of electromagnetic radiation arranged according to their wavelength or frequency.

• X-Ray has a very short wavelength, ranging from about 0.01 to 10 nanometers.

• Ultra Violet comes next with wavelengths between 10 and 400 nanometers.

• Visible light is just a small portion of the spectrum that our eyes can perceive, with wavelengths from approximately 400 to 700 nanometers.

• Near Infrared wavelengths range from about 700 nanometers to 1 micrometer. Thermal Infrared has wavelengths from about 3 micrometers to 30 micrometers.

Thus, the increasing order of wavelength is X-Ray, Ultra Violet, Visible, Near IR, and Thermal IR.

Image interpretation elements help in understanding and deciphering satellite images or aerial photographs.

• Association involves the relationship between different objects or features and is complex since it needs a deeper understanding of the landscape.

• Aspect refers to the direction that a slope faces. It's a more specific feature that requires understanding of the surrounding environment.

• Pattern denotes the spatial arrangement of objects. Texture represents the visual roughness or smoothness of an image.

• Location is the simplest, referring to the geographical position of a feature.
Therefore, the decreasing order of complexity is Association, Aspect, Pattern, Texture, and Location.

Metamorphic rocks are formed under heat and pressure conditions. Their grade indicates the intensity of these conditions.

• Slate forms under the lowest metamorphic conditions and is characterized by its fine grain.

• Phyllite is slightly higher in grade than slate, having a silky sheen.

• Gneiss is higher in grade, with distinct banding due to the separation of mafic and felsic minerals.

• Migmatite is at the highest grade before melting, comprising both metamorphic and igneous components.

So, the increasing metamorphic grade order is Slate, Phyllite, Gneiss, and Migmatite.

Fractional crystallization of magma involves the systematic cooling and solidification of different minerals at specific temperatures.

• Olivine crystallizes at the highest temperatures. Pyroxene follows olivine as the temperature drops. Amphibole crystallizes at a still lower temperature.

• Biotite crystallizes at one of the lowest temperatures in this sequence.

This sequence demonstrates the Bowen's reaction series, which describes the order of mineral crystallization from magma.

Coal is a sedimentary rock, and its type is determined by its carbon content, which increases with maturity.

• Peat is the precursor to coal, with the lowest carbon content and highest moisture content.

• Lignite or brown coal is slightly higher in carbon content than peat.

• Sub-bituminous is a transition between lignite and bituminous with a higher carbon content.

• Bituminous is soft coal with even more carbon.

• Anthracite is hard coal with the highest carbon content and purity.
Thus, the increasing order of carbon content is Peat, Lignite, Sub-bituminous, Bituminous, and Anthracite.