UPSC CAPF

1. Which one of the following is the audible range of hearing for humans

Which one of the following is the audible range of hearing for humans ?

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20 kHz – 200 kHz
20 Hz – 20 kHz
20 Hz – 35 kHz
20 Hz – 40 kHz
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UPSC CAPF – 2024
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The correct option is B. The generally accepted audible range of hearing for young, healthy humans is from 20 Hz to 20 kHz.
– ‘Hz’ stands for Hertz, which is a unit of frequency (cycles per second).
– ‘kHz’ stands for kilohertz, which is 1000 Hertz.
– The lower limit of human hearing is around 20 Hz, and the upper limit is around 20,000 Hz (20 kHz).
Hearing range can vary between individuals and typically decreases with age, especially at higher frequencies. Frequencies below 20 Hz are called infrasound, and frequencies above 20 kHz are called ultrasound. Humans cannot hear these sounds, although some animals can.

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2. Which one among the following is used in the manufacture of ultra-viol

Which one among the following is used in the manufacture of ultra-violet protective glasses ?

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Aluminium oxide
Tungsten oxide
Molybdenum oxide
Cerium oxide
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The correct option is D. Cerium oxide is commonly used as an additive in glass manufacturing to absorb ultraviolet radiation, thus producing ultra-violet protective glasses.
– Certain metal oxides, when added to glass, can impart specific optical properties, including the absorption of UV light.
– Cerium oxide (CeO₂) is particularly effective at absorbing UV radiation across the spectrum relevant for protecting eyes and materials from UV damage.
While other oxides can affect glass properties, cerium oxide is specifically known and widely used for its UV absorption capabilities in glasses for spectacles, laboratory ware, and architectural uses.

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3. Which one among the following is an example of endothermic process ?

Which one among the following is an example of endothermic process ?

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Combustion of carbon
Mixing acid and alkali
Photosynthesis
Respiration
This question was previously asked in
UPSC CAPF – 2024
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The correct option is C. Photosynthesis is an example of an endothermic process because it requires energy input (light energy) from the surroundings to proceed.
– An endothermic process absorbs heat or energy from the surroundings. The temperature of the surroundings typically decreases.
– An exothermic process releases heat or energy into the surroundings. The temperature of the surroundings typically increases.
– Photosynthesis converts light energy into chemical energy stored in glucose: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Light Energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.
Combustion of carbon, mixing acid and alkali (neutralization), and respiration are all exothermic processes, releasing energy.

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4. Which one among the following statements with respect to the atomic nu

Which one among the following statements with respect to the atomic number of an atom is correct ?

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The number of neutrons is same as atomic number
The sum of electrons and neutrons is same as atomic number
The number of protons is same as atomic number
The sum of protons and neutrons is same as atomic number
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UPSC CAPF – 2024
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The correct option is C. The atomic number of an atom is defined as the number of protons in the nucleus of that atom.
– Atomic number (Z) is a fundamental property of an element that uniquely identifies it.
– It represents the number of positive charges (protons) in the nucleus.
– In a neutral atom, the number of electrons is equal to the number of protons.
The mass number (A) of an atom is the sum of the number of protons and neutrons in the nucleus. Isotopes of an element have the same atomic number (same number of protons) but different mass numbers (different numbers of neutrons).

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5. Which among the following are the main ingredients for manufacturing o

Which among the following are the main ingredients for manufacturing of glass ?

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Silica, sodium carbonate, borax, alumina and cullets
Iron oxide, lead, sodium bicarbonate, alumina and cullets
Magnesium carbonate, alumina, silica and cullets
Iron oxide, sodium, alumina, silica and cullets
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UPSC CAPF – 2024
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The correct option is A. The main ingredients for manufacturing common glass (soda-lime glass) are silica, sodium carbonate (soda ash), and calcium carbonate (limestone). Option A includes silica and sodium carbonate, along with other common additives and components used in glass manufacturing.
– Silica (sand) is the primary component, forming the glass structure.
– Sodium carbonate (soda ash) is added to lower the melting point of silica. It decomposes to sodium oxide (Na₂O) during heating.
– Calcium carbonate (limestone) is added to improve durability and prevent the glass from dissolving in water. It decomposes to calcium oxide (CaO) during heating.
– Alumina (aluminium oxide) is a common additive to increase strength, chemical resistance, and reduce devitrification.
– Borax (sodium borate) is used in the manufacture of borosilicate glass, which has high thermal resistance. Its presence in option A suggests a broader view of glass manufacturing ingredients beyond just standard soda-lime glass.
– Cullets are recycled glass added to the batch mixture. They act as a flux, reducing the melting temperature and saving energy.
While standard soda-lime glass primarily uses silica, sodium carbonate, and calcium carbonate, option A provides a list that includes key primary components and common additives like alumina and borax (for specific glass types), along with cullets which are universally used in modern glass production. Options B, C, and D contain inaccuracies like elemental sodium or less common primary components.

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6. Which among the following is correct with respect to bond formation in

Which among the following is correct with respect to bond formation in an ethyne molecule ?

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Carbon-Carbon single bond
Carbon-Carbon double bond
Carbon-Carbon triple bond
Carbon-Hydrogen double bond
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UPSC CAPF – 2024
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Ethyne is an organic compound with the chemical formula C₂H₂. It belongs to the alkyne family of hydrocarbons, which are characterized by the presence of a carbon-carbon triple bond. The structure of ethyne is H-C≡C-H. Each carbon atom is bonded to one hydrogen atom via a single covalent bond and to the other carbon atom via a triple covalent bond. Alkanes have single bonds (C-C), alkenes have double bonds (C=C), and alkynes have triple bonds (C≡C) between carbon atoms.
Hydrocarbons are classified based on the types of bonds between carbon atoms. Alkanes have only single bonds, alkenes have at least one double bond, and alkynes have at least one triple bond. Ethyne is the simplest alkyne.
A carbon-carbon triple bond consists of one sigma bond and two pi bonds. The carbon atoms in ethyne are sp-hybridized, resulting in a linear geometry around the triple bond. Ethyne is also commonly known as acetylene and is used as a fuel in welding and cutting.

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7. Water is a good solvent for dissolving ionic compounds because

Water is a good solvent for dissolving ionic compounds because

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It has a high specific heat
It has no colour
It has a high dipole moment
It has a high boiling point
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UPSC CAPF – 2024
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Water is an excellent solvent for ionic compounds because it is a polar molecule with a high dipole moment. An ionic compound is held together by strong electrostatic forces between positive and negative ions in a crystal lattice. Water molecules, being polar, have a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. When an ionic compound is placed in water, the positive ends of water molecules are attracted to the negative ions, and the negative ends are attracted to the positive ions. These attractive forces between water molecules and ions (ion-dipole interactions) are strong enough to overcome the lattice energy of the ionic compound, causing the ions to separate and become surrounded by water molecules (hydration). A high dipole moment indicates strong polarity, which is crucial for this process. High specific heat, no colour, and high boiling point are characteristics of water but are not the primary reason for its ability to dissolve ionic compounds.
Water’s ability to dissolve ionic compounds stems primarily from its strong polarity and high dipole moment, which allows it to hydrate (surround and separate) the positive and negative ions.
The process of dissolving an ionic compound in water is called dissociation and hydration. The hydrated ions are dispersed throughout the solution. Water is often referred to as the “universal solvent” because of its ability to dissolve a wide range of substances, including many ionic and polar covalent compounds.

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8. The isotope of which one among the following elements is used in the t

The isotope of which one among the following elements is used in the treatment of cancer ?

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Uranium
Cobalt
Iodine
Fluorine
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UPSC CAPF – 2024
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Several radioactive isotopes are used in the treatment of cancer, primarily in radiotherapy. Cobalt-60 is a widely used radioisotope that emits gamma rays, which are used in external beam radiotherapy machines (sometimes called “cobalt therapy”). Iodine-131 is used for internal radiotherapy, specifically in the treatment of thyroid cancer because the thyroid gland preferentially absorbs iodine. Uranium is used in nuclear power and weapons, not typically for direct cancer treatment. Fluorine-18 is a positron-emitting isotope used as a tracer in PET scans (Positron Emission Tomography), which is a diagnostic imaging technique, not a treatment. While Iodine-131 is used, Cobalt-60 is perhaps the most general and well-known example of a radioisotope used in radiotherapy for a wide range of cancers. Therefore, Cobalt is a correct answer.
Radioisotopes of certain elements are used in cancer treatment, particularly radiotherapy, to target and destroy cancer cells using emitted radiation. Cobalt-60 is a common example for external radiotherapy.
Other isotopes used in cancer therapy include Iridium-192 and Cesium-137 (brachytherapy), Gold-198 (colloidal gold therapy), and Phosphorus-32 (for polycythemia vera and chronic myeloid leukemia). Targeted alpha therapy uses isotopes that emit alpha particles (e.g., Radium-223, Actinium-225) linked to targeting molecules.

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9. Which one among the following statements about matter is NOT correct ?

Which one among the following statements about matter is NOT correct ?

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On increasing the temperature of solids, the kinetic energy of particles increases
The maximum temperature at which a solid melts to become a liquid at atmospheric pressure is called its melting point
Particles of steam have more energy than water at 100°C
Direct change of gas to solid is called deposition
This question was previously asked in
UPSC CAPF – 2024
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Let’s examine each statement:
A) On increasing the temperature of solids, the kinetic energy of particles increases. This is correct. Temperature is a measure of the average kinetic energy of the particles.
B) The maximum temperature at which a solid melts to become a liquid at atmospheric pressure is called its melting point. For a pure crystalline solid at constant pressure, melting occurs *at* a specific temperature called the melting point. Saying it is the *maximum* temperature at which it melts is imprecise or incorrect. Above the melting point, the substance is in the liquid state. For impure or amorphous solids, melting can occur over a range of temperatures, but the term ‘melting point’ usually refers to the start of the melting range or the specific temperature for pure substances. The phrasing “maximum temperature at which a solid melts” is misleading for a pure substance and not a standard definition for the melting point.
C) Particles of steam have more energy than water at 100°C. This is correct. When water boils at 100°C, it absorbs latent heat of vaporization to change state into steam at the same temperature. This latent heat increases the internal energy (primarily potential energy related to intermolecular forces) of the particles in the gaseous state compared to the liquid state at the same temperature.
D) Direct change of gas to solid is called deposition. This is correct. The phase transition from gas directly to solid is known as deposition or desublimation. The reverse process, solid to gas, is called sublimation.
Therefore, statement B is the incorrect statement due to its inaccurate phrasing regarding the melting point of a solid.
Understanding the states of matter, phase transitions, and the relationship between temperature, energy, and particle motion. Melting point is the specific temperature at which a pure crystalline solid melts at a given pressure.
Phase transitions like melting, boiling, sublimation, condensation, freezing, and deposition occur at specific temperatures (at constant pressure) for pure substances, involving the absorption or release of latent heat. The kinetic energy of particles is related to temperature within a single phase, while potential energy changes significantly during phase transitions.

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10. Which one among the following does NOT have any linkage with the pheno

Which one among the following does NOT have any linkage with the phenomenon of electromagnetic induction ?

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Electric transformer
Induction cooker
Galvanometer
Electron microscope
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UPSC CAPF – 2024
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Electromagnetic induction is the phenomenon where a change in magnetic flux through a circuit induces an electromotive force (EMF) or voltage, which can drive a current. This is described by Faraday’s Law of Induction. An electric transformer works entirely on the principle of mutual induction between coils. An induction cooker heats a metal pan by inducing eddy currents within it using a changing magnetic field, which is a direct application of electromagnetic induction. A galvanometer is a device used to detect and measure electric current. Its operation is typically based on the motor principle: a current-carrying coil placed in a magnetic field experiences a torque, causing it to deflect. This principle is derived from the Lorentz force on moving charges in a magnetic field, and while related to electromagnetism, it is distinct from electromagnetic *induction* (generating voltage/current from changing magnetic fields). An electron microscope uses magnetic lenses to focus beams of electrons. This focusing action is achieved by the Lorentz force exerted by magnetic fields on the moving electrons, not electromagnetic induction. However, considering the options, the galvanometer’s operating principle (motor effect) is most clearly and fundamentally distinct from electromagnetic induction, which is the basis of the transformer and induction cooker. The electron microscope uses magnetic fields to steer charges, a direct application of Lorentz force. Out of C and D, C (Galvanometer) is the most conventional example of a device whose core principle is the motor effect rather than induction.
Electromagnetic induction is the process of generating voltage/current through changing magnetic fields (Faraday’s Law). The motor principle (force on a current in a magnetic field) and the Lorentz force (force on a moving charge in a magnetic field) are related but distinct principles of electromagnetism. Transformers and induction cookers directly rely on electromagnetic induction. A galvanometer primarily relies on the motor principle.
The relationship between the motor principle and electromagnetic induction is linked by Lenz’s Law and energy conservation. However, the fundamental operational principle of a galvanometer is the torque on a current loop, not the generation of current by changing flux.

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