UPSC NDA-1 Archives

11. An object is placed 10 cm in front of a convex lens of focal length 15

An object is placed 10 cm in front of a convex lens of focal length 15 cm. The image produced will be

Real and magnified

Virtual and magnified

Virtual and reduced in size

Real and reduced in size

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UPSC NDA-1 – 2015

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For a convex lens, the focal length ($f$) is positive. Given $f = +15$ cm. The object is placed at $u = -10$ cm (negative sign indicates it’s in front of the lens). Using the lens formula $1/f = 1/v – 1/u$:
$1/15 = 1/v – 1/(-10)$
$1/15 = 1/v + 1/10$
$1/v = 1/15 – 1/10$
$1/v = (2 – 3)/30$
$1/v = -1/30$
$v = -30$ cm
The image distance $v$ is -30 cm. A negative image distance for a lens indicates that the image is formed on the same side as the object, which means it is a virtual image.
The magnification ($m$) is given by $m = v/u$:
$m = (-30) / (-10) = +3$
The positive magnification indicates the image is erect (virtual images are always erect). The magnitude of magnification $|m| = 3$ is greater than 1, indicating that the image is magnified (larger than the object).
Therefore, the image is virtual and magnified.

Applying the lens formula and magnification formula to determine the nature and size of the image formed by a convex lens for a given object position.

For a convex lens, when the object is placed between the optical center and the focal point (i.e., $u < f$), a virtual, erect, and magnified image is formed on the same side as the object. In this case, $u=10$ cm and $f=15$ cm, so $u < f$, fitting this scenario.

12. A ray of light when refracted suffers change in velocity. In this cont

A ray of light when refracted suffers change in velocity. In this context, which one among the following statements is correct ?

Velocity increases as the ray passes from a rarer to a denser medium

Velocity decreases as the ray passes from a denser to a rarer medium

Velocity decreases as the ray passes from a rarer to a denser medium

Change of velocity does not depend on the nature of medium

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UPSC NDA-1 – 2015

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When a ray of light passes from a rarer medium (like air) to a denser medium (like glass or water), its speed decreases. This change in speed is related to the refractive index of the medium; a denser medium has a higher refractive index, causing light to slow down. Conversely, when light passes from a denser medium to a rarer medium, its speed increases.

Understanding how the speed of light changes when it undergoes refraction from one medium to another.

The relationship between the speed of light ($v$), the speed of light in vacuum ($c$), and the refractive index ($n$) of a medium is given by $v = c/n$. A denser medium has a higher refractive index ($n$), resulting in a lower speed of light ($v$). A rarer medium has a lower refractive index, resulting in a higher speed of light.

13. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the Lists :

List I
(Physical quantity)
List II
(Unit)

A. Distance	1. Mole
B. Amount of material	2. Coulomb
C. Amount of electrical charge	3. Light year
D. Energy	4. Watt hour

3 1 2 4

3 2 1 4

4 2 1 3

4 1 2 3

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UPSC NDA-1 – 2015

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Matching the physical quantities with their appropriate units:
A. Distance – 3. Light year (A light-year is the distance light travels in one year, used for astronomical distances).
B. Amount of material – 1. Mole (The mole is the SI unit for amount of substance).
C. Amount of electrical charge – 2. Coulomb (The Coulomb is the SI unit for electric charge).
D. Energy – 4. Watt hour (A watt-hour is a unit of energy, calculated as power (Watts) multiplied by time (hours). It is commonly used for measuring electrical energy).
This results in the sequence 3 1 2 4, which matches option A.

Matching common physical quantities with their standard or relevant units.

Other common units for distance include meters, kilometers, miles, etc. Other common units for energy include Joules (the SI unit), calories, kilowatt-hours (1 kWh = 1000 Wh). The units provided in List II are all valid units for the corresponding quantities, although some are not SI units (like light-year or watt-hour).

14. In plants, which one of the following gases is released during Photosy

In plants, which one of the following gases is released during Photosynthesis ?

Carbon dioxide

Oxygen

Hydrogen

Methane

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UPSC NDA-1 – 2015

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Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll pigment. The overall equation for photosynthesis is: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Light Energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$. The gases involved as reactants are Carbon dioxide ($\text{CO}_2$), and the gas released as a product is Oxygen ($\text{O}_2$).

Knowing the inputs and outputs of the photosynthesis process.

Plants take in carbon dioxide from the atmosphere and water from the soil. Using light energy, they convert these into glucose (a sugar) and release oxygen into the atmosphere. This process is vital for maintaining the Earth’s atmosphere composition and providing the basis for most food chains.

15. Which one of the following is the smallest unit showing the properties

Which one of the following is the smallest unit showing the properties of life such as capacity for metabolism, response to the environment, growth and reproduction ?

Gene

Chromosome

Nucleus

Cell

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UPSC NDA-1 – 2015

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The cell is considered the fundamental structural and functional unit of life. It is the smallest unit that exhibits all the basic properties of life, including metabolism, response to stimuli, growth, and reproduction (at the cellular level, via division). Genes, chromosomes, and the nucleus are components within a cell and cannot independently perform all life processes.

Understanding the concept of the cell as the basic unit of life.

Genes are units of heredity made of DNA. Chromosomes are structures containing coiled DNA, carrying genetic information. The nucleus is an organelle containing the cell’s genetic material in eukaryotes. All these components work within the framework of a cell to carry out life functions.

16. Which one of the following irrigation canals is the most important in

Which one of the following irrigation canals is the most important in terms of area coverage in Haryana ?

Bhakra canal

The Western Yamuna canal

Jawaharlal Nehru canal

Gurgaon canal

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UPSC NDA-1 – 2015

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The Western Yamuna Canal (WYC) system is the largest and oldest irrigation system in Haryana, covering the widest area for irrigation purposes in the state.

Identifying the most important irrigation project in a specific geographical region based on its coverage area.

The Western Yamuna Canal originates from the Tajewala barrage in Haryana. It irrigates a large part of Haryana, including districts like Ambala, Karnal, Rohtak, Hissar, and Jind. While the Bhakra Canal also irrigates parts of Haryana, the Western Yamuna Canal system is generally considered more extensive within the state.

17. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the Lists :

List I
(Place)

List II
(Industry)

A. Jabalpur	1. Petro-chemical industry
B. Bengaluru	2. IT industry
C. Mathura	3. Paper industry
D. Ballarpur	4. Automobile industry

Code :

A-4, B-1, C-2, D-3

A-3, B-2, C-1, D-4

A-4, B-2, C-1, D-3

A-3, B-1, C-2, D-4

This question was previously asked in

UPSC NDA-1 – 2015

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The correct matching is:
A. Jabalpur – 4. Automobile industry (Specifically, Ordnance Factory Jabalpur produces vehicles)
B. Bengaluru – 2. IT industry (Known as the Silicon Valley of India)
C. Mathura – 1. Petro-chemical industry (Location of a major oil refinery)
D. Ballarpur – 3. Paper industry (A major paper manufacturing centre in Maharashtra)
Matching these pairs gives A-4, B-2, C-1, D-3, which corresponds to option C.

This question tests knowledge of the location of major industries in India.

Bengaluru is a global hub for information technology. The Mathura Refinery is one of the largest refineries owned by Indian Oil Corporation. Ballarpur Industries Limited (BILT) has a significant paper manufacturing plant in Ballarpur. Jabalpur’s industrial profile includes defence production, including vehicles, and other manufacturing activities.

18. Rain shadow effect is associated with

Rain shadow effect is associated with

Cyclonic rainfall

Orographic rainfall

Convectional rainfall

Frontal rainfall

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UPSC NDA-1 – 2015

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The correct answer is Orographic rainfall. The rain shadow effect is a direct consequence of orographic lift and precipitation.

Orographic rainfall occurs when moist air is forced to rise over a mountain range. As the air rises, it cools, condenses, and precipitates on the windward side of the mountains. By the time the air descends on the leeward side, it has lost most of its moisture and warms up, creating a dry area known as a rain shadow.

Cyclonic rainfall is associated with low-pressure systems (cyclones). Convectional rainfall occurs due to intense heating of the ground, causing air to rise, cool, and condense. Frontal rainfall occurs where two different air masses meet along a front. Only orographic rainfall directly leads to the distinct wet windward side and dry leeward (rain shadow) side of a mountain range.

19. The chemical used as a fixer/developer in photography is

The chemical used as a fixer/developer in photography is

Sodium sulphate

Sodium sulphide

Sodium thiosulphate

Sodium sulphite

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UPSC NDA-1 – 2015

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The correct answer is Sodium thiosulphate. Sodium thiosulphate (Na₂S₂O₃), commonly known as “hypo”, is widely used as a fixer in traditional silver-halide photography.

In photography, after development (where exposed silver halide is converted to metallic silver), the fixer bath is used to remove the *unexposed* silver halide crystals from the film or paper. Sodium thiosulphate dissolves these unexposed crystals, making the image permanent and no longer sensitive to light. While Sodium sulphite can be a component of developer solutions (as a preservative), Sodium thiosulphate is the primary chemical used as a *fixer*. Given the “fixer/developer” phrasing and the options, sodium thiosulphate is the most definitive answer for a chemical used in one of these key steps, specifically fixing.

Developer solutions typically contain chemicals like Metol and Hydroquinone (reducing agents), Sodium sulphite (preservative), Borax (accelerator), and Potassium bromide (restrainer). Fixer solutions typically contain Sodium thiosulphate or Ammonium thiosulphate.

20. The cleaning action of soap and detergent in water is due to the forma

The cleaning action of soap and detergent in water is due to the formation of

Micelle

Salt

Base

Acid

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UPSC NDA-1 – 2015

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The correct answer is Micelle. Soap and detergent molecules form structures called micelles in water, which are responsible for their cleaning action.

Soap and detergent molecules have a hydrophilic (water-attracting) head and a hydrophobic (oil/grease-attracting) tail. In water, these molecules aggregate into spherical structures called micelles, where the hydrophobic tails are oriented inward, away from the water, and the hydrophilic heads are oriented outward, in contact with the water. Oily or greasy dirt particles get trapped within the hydrophobic core of these micelles and are thus suspended in water, allowing them to be washed away.

While soap itself is a salt (sodium or potassium salt of fatty acids), and soap solutions are typically slightly basic due to hydrolysis, their primary cleaning mechanism relies on micelle formation and the ability of micelles to emulsify fats and oils. Acids are not relevant to the cleaning action of soaps and detergents.