UPSC NDA-1 Archives

21. When light is scattered by a molecule and the frequency of the scatter

When light is scattered by a molecule and the frequency of the scattered light is changed, this phenomenon is called

Rayleigh scattering.

Raman effect.

Photoelectric effect.

Rutherford scattering.

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The phenomenon where light is scattered by a molecule and the frequency of the scattered light is changed is called B) Raman effect.

– Scattering of light is the process where light is deflected by particles in the medium.
– When the scattering is elastic, the frequency of the scattered light is the same as the incident light (e.g., Rayleigh scattering).
– When the scattering is inelastic, there is an exchange of energy between the light photon and the scattering molecule, resulting in a change in the frequency (and wavelength) of the scattered light.
– The Raman effect is an example of inelastic scattering of light by molecules, where the scattered light can have frequencies shifted up or down from the incident frequency, corresponding to transitions between vibrational or rotational energy levels of the molecule.

– Rayleigh scattering is elastic scattering by particles much smaller than the wavelength of light.
– Photoelectric effect is the emission of electrons from a material when light shines on it.
– Rutherford scattering is the scattering of alpha particles by atomic nuclei, used in the discovery of the atomic nucleus.

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22. The sound created in a big hall persists because of the repeated refle

The sound created in a big hall persists because of the repeated reflections. The phenomenon is called

Reverberation.

Dispersion.

Refraction.

Diffraction.

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The phenomenon where sound persists in a big hall because of repeated reflections is called A) Reverberation.

– Reflection of sound waves occurs when they bounce off surfaces.
– In an enclosed space, sound waves reflect repeatedly from walls, ceilings, and other surfaces.
– Reverberation is the persistence of sound after the source has stopped, caused by these multiple reflections delaying the sound’s decay.

– Dispersion is the splitting of waves based on wavelength (e.g., light into colours).
– Refraction is the bending of waves as they pass from one medium to another.
– Diffraction is the bending of waves around obstacles or through openings.
– While reflection is the mechanism, the *persistence* of sound due to these multiple reflections is specifically termed reverberation. Excessive reverberation can make sound unclear in large halls.

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23. Which one of the following formulas does * not * represent electrical

Which one of the following formulas does *not* represent electrical power?

I²R

IR²

V²/R

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The formula that does *not* represent electrical power is B) IR².

– Electrical power (P) is the rate at which electrical energy is transferred or consumed.
– The basic formulas for power are P = VI, where V is voltage and I is current.
– Using Ohm’s Law (V = IR), we can derive other forms:
– Substituting V = IR into P = VI gives P = (IR) * I = I²R. (Option A)
– Substituting I = V/R into P = VI gives P = V * (V/R) = V²/R. (Option D)
– Option C, VI, is also a standard formula for power.

– The formula IR² is incorrect. The power dissipated by a resistor is I²R.
– The unit of power is the Watt (W).

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24. A current of 1·0 A is drawn by a filament of an electric bulb for 10 m

A current of 1·0 A is drawn by a filament of an electric bulb for 10 minutes. The amount of electric charge that flows through the circuit is

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0·1 C

10 C

600 C

800 C

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The correct answer is C) 600 C. The amount of electric charge (Q) that flows through a circuit is given by the product of the current (I) and the time (t), i.e., Q = I × t.

– Current (I) is given as 1.0 A.
– Time (t) is given as 10 minutes.
– Time must be converted to seconds for the calculation: 10 minutes * 60 seconds/minute = 600 seconds.
– Q = 1.0 A * 600 s = 600 Coulombs.

– The unit of electric charge is the Coulomb (C).
– The unit of electric current is the Ampere (A), which is defined as one Coulomb per second (C/s).

25. A glass prism splits white light into different colours. This phenomen

A glass prism splits white light into different colours. This phenomenon is called dispersion of light by prism. Which one of the following statements is correct ?

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Red light will deviate the most and it is because of the reflection of light.

Violet light will deviate the most and it is because of the refraction of light.

Red light will deviate the most and it is because of the refraction of light.

Violet light will deviate the most and it is because of the reflection of light.

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The correct statement is B) Violet light will deviate the most and it is because of the refraction of light.

– Dispersion is the splitting of white light into its constituent colours when it passes through a prism.
– This occurs because the refractive index of the prism material is different for different wavelengths (colours) of light; this phenomenon is called refraction.
– The deviation angle for a given colour depends on the refractive index for that colour.
– Violet light has the shortest wavelength and the highest refractive index in glass, causing it to bend the most.
– Red light has the longest wavelength and the lowest refractive index in glass, causing it to bend the least.

– The order of colours in the spectrum from least deviated to most deviated is Red, Orange, Yellow, Green, Blue, Indigo, Violet (VIBGYOR in reverse).
– Dispersion is a phenomenon of refraction, not reflection. Reflection is the bouncing back of light from a surface.

26. Which one of the following statements is * not * correct for light ray

Which one of the following statements is *not* correct for light rays ?

Light travels at different speeds in different media.

Light travels at almost 300 million metres per second in air.

Light speeds down as it leaves a water surface and enters the air.

Light speeds up as it leaves a glass surface and enters the air.

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The correct statement that is *not* correct is C) Light speeds down as it leaves a water surface and enters the air.

– The speed of light changes as it passes from one medium to another.
– Light travels fastest in a vacuum (approximately 3 x 10⁸ m/s).
– The speed of light is slower in optically denser media (like water or glass) than in optically less dense media (like air or vacuum).

– A) is correct: The speed of light depends on the refractive index of the medium.
– B) is correct: The speed of light in air is very close to its speed in vacuum.
– C) is incorrect: Water is optically denser than air. When light moves from a denser medium (water) to a less dense medium (air), its speed *increases*.
– D) is correct: Glass is optically denser than air. When light moves from a denser medium (glass) to a less dense medium (air), its speed *increases*.

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27. In a dicot pot herb, vaseline/vegetable oil was applied on the upper s

In a dicot pot herb, vaseline/vegetable oil was applied on the upper surface of one leaf (Experimental leaf 1) and on the lower surface of another leaf (Experimental leaf 2). Vaseline/Vegetable oil was not applied on the control leaf. The plant was deliberately not watered for several days. Which leaf will dry up last?

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Experimental leaf 1

Experimental leaf 2

Control leaf

All the leaves will dry up simultaneously

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The correct answer is B) Experimental leaf 2. Applying vaseline/vegetable oil to the lower surface of the leaf blocks most of the stomata, significantly reducing water loss through transpiration.

– Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.
– Stomata are pores on the leaf surface, primarily on the lower surface in dicots, that regulate gas exchange and transpiration.
– Blocking stomata reduces the rate of transpiration and thus water loss.

– Experimental leaf 1 has vaseline on the upper surface, leaving most stomata on the lower surface open, so it will lose water almost as fast as the control leaf.
– The control leaf loses water normally from both surfaces (mainly lower).
– Since Experimental leaf 2 loses the least amount of water due to blocked stomata on the lower surface, it will dry up last among the three leaves when the plant is not watered.

28. The gaseous product of a process in plants is a requirement for anothe

The gaseous product of a process in plants is a requirement for another vital process that releases energy. Given below are four combinations of the process and product. Identify the correct answer.

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Respiration and Nitric oxide

Transpiration and Water vapour

Photosynthesis and Oxygen

Germination and Carbon dioxide

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The correct answer is C) Photosynthesis and Oxygen. Oxygen is a gaseous product of photosynthesis and is a requirement for aerobic respiration, a vital process that releases energy in most organisms, including plants.

– Photosynthesis is the process by which plants convert light energy into chemical energy (glucose) using carbon dioxide and water, releasing oxygen as a byproduct.
– Respiration is the process by which organisms break down organic molecules (like glucose) to release energy. Aerobic respiration requires oxygen and produces carbon dioxide and water.
– The question describes a gaseous product (oxygen from photosynthesis) being a requirement (for respiration) of a process that releases energy.

– Transpiration produces water vapour, which is not a requirement for energy release.
– Nitric oxide is not a standard product of respiration or a requirement for energy release in typical metabolic pathways.
– Germination is a process, not a gaseous product. While respiration provides energy for germination, carbon dioxide is a product of respiration, not a requirement for it.

29. Transformation of meristematic cells into specific permanent tissues o

Transformation of meristematic cells into specific permanent tissues occurs by the process of

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Cell differentiation.

Cell division.

Cell multiplication.

Cell regeneration.

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The correct answer is A) Cell differentiation. Cell differentiation is the process by which a less specialized cell becomes a more specialized cell type.

– Meristematic cells are undifferentiated plant cells capable of active division.
– Permanent tissues are composed of cells that have undergone differentiation and often lose the ability to divide or divide slowly, performing specific functions.
– Differentiation involves changes in cell structure and function leading to specialization.

– Cell division (or multiplication) is the process by which a parent cell divides into two or more daughter cells, increasing the number of cells but not necessarily leading to specialization.
– Cell regeneration refers to the regrowth of damaged or missing tissues or organs.

30. Squamous epithelial cells are found in the inner lining of

Squamous epithelial cells are found in the inner lining of

Oesophagus.

Small intestine.

Ducts of salivary gland.

Kidney.

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The correct answer is A) Oesophagus. The inner lining (mucosa) of the oesophagus in mammals is composed of non-keratinized stratified squamous epithelium.

– Squamous epithelium is characterized by flattened cells.
– Stratified squamous epithelium consists of multiple layers of squamous cells and is found in locations requiring protection against abrasion.
– The oesophagus is a tube that transports food from the mouth to the stomach, and its lining is subject to friction from food passage, making stratified squamous epithelium suitable.

– The small intestine is lined with simple columnar epithelium with microvilli, adapted for absorption.
– Ducts of salivary glands are typically lined with cuboidal or columnar epithelium.
– The kidney contains various epithelial types; Bowman’s capsule has simple squamous epithelium, while kidney tubules are lined with cuboidal epithelium. The oesophagus is a classic example of a lumen’s inner lining being primarily composed of stratified squamous epithelium.

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