Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Statement 1 is correct: In November 2006, the Defence Research and Development Organisation (DRDO) of India conducted a successful test of the Prithvi Air Defence (PAD) system, which used the Prithvi-II missile as an interceptor to destroy an incoming target missile. The Prithvi-II missile has been instrumental in validating India’s BMD technologies, ensuring readiness to protect against ballistic missile threats. This test marked a significant milestone in India’s ballistic missile defence program.

Statement 2 is correct: While the primary role of the Prithvi-II is as a surface-to-surface missile but it has been adapted for air defense purposes also. It is part of India’s Ballistic Missile Defense (BMD) system, which is designed to protect major cities from ballistic missile attacks.

Explanation

The Galileo Project is a multi-satellite navigation system being developed by the European Union (EU). Galileo consists of 24 satellites orbiting Earth at an altitude of 23,000 km. The signals of Galileo are freely transmitted to anyone who has a device capable of receiving its signals (e.g., smartphone). Galileo is four times more accurate than GPS providing 1 meter accuracy and a broad range of services. It is designed to provide an independent global positioning system (GPS) for civilian and commercial use, reducing reliance on GPS systems controlled by other countries, such as the United States. Galileo aims to offer highly accurate and reliable positioning and timing information worldwide, supporting applications in transportation, telecommunications, and other critical sectors.

Explanation

Statement 1 is incorrect: The frequency of sound produced by a flute is inversely proportional to its length. A shorter flute produces sound waves of higher frequency (higher pitch), while a longer flute produces sound waves of lower frequency (lower pitch).

Statement 2 is incorrect: Sound (or seismic waves) in rocks travels in both longitudinal (P-waves) and transverse (S-waves) forms. Longitudinal waves compress and expand the material, while transverse waves move the material perpendicular to the direction of propagation of the wave.

Explanation

Option (a) is correct: Computed Tomography (CT), also known as a CT scan, uses X-rays to create detailed cross-sectional images of the internal structures of the human body. The X-rays rotate around the body, and a computer processes the data to generate 3D or 2D images. Options (b), (c) and (d) are incorrect:

Sound waves are used in ultrasound imaging not in CT Scans. Magnetic resonance is associated with MRI, which uses magnetic fields and radio waves, not X-rays. Radio isotopes are used in nuclear medicine, such as PET scans.

Explanation

Option (d) is correct: Crookes glass is a type of glass that can absorb and block ultraviolet (UV) rays. It is specially designed to cut off UV radiation while allowing visible light to pass through. This makes it useful in applications where protection from UV light is needed, such as in certain laboratory equipment or sun protection glasses. Options (a), (b) and (c) are incorrect: Soda glass is a common type of glass used for general purposes, but it does not have UV-blocking properties. Pyrex glass is known for its heat resistance and is used in laboratory equipment but does not specifically block UV rays. Jena glass is a type of glass with special properties, mainly used in scientific instruments, but it is not specifically designed to block ultraviolet rays.

Explanation

Selenium is a semiconductor, meaning it has electrical conductivity that lies between that of metals and insulators. Its conductivity increases with exposure to light, making it useful in solar cells and photoelectric applications. Therefore, selenium is not a poor conductor of electricity.

Explanation

Option (c) is correct: Zinc oxide (ZnO) is commonly referred to as philosopher’s wool. It is known as philosopher wool due to its wool-like texture. This name comes from the historical belief that zinc oxide could be produced by heating zinc metal in air, and it was once used by alchemists in their experiments. Zinc oxide is a white powder with applications in Cosmetics (UV-blocking in sunscreens), Rubber (activator in vulcanization), Paints (pigment, mildew-resistant) and Pharmaceuticals (antiseptic in ointments). Options (a), (b) and (d) are incorrect:

Zinc bromide (ZnBr₂) is used in dry cell batteries and photography. Zinc nitrate (Zn(NO₃)₂) is used in fertilizers and as a laboratory reagent. Zinc chloride (ZnCl₂) is used in chemical production and water treatment. None of these compounds are associated with the term "philosopher’s wool," which refers to zinc oxide (ZnO).

Explanation

Option (b) is correct: German silver does not contain any silver at all. Alloy of copper (60%), nickel (20%), and zinc (20%). No actual silver content. Known for hardness, corrosion resistance, and silver-like appearance. Commonly used in jewelry, musical instruments, and coins. Options (a), (c) and (d) are incorrect:

Horn silver (also known as silver chloride, AgCl), gray, heavy halide mineral. Found in oxidized zones of silver-bearing veins. It is associated with silver and silver related minerals. Ruby silver: Collective term for pyrargyrite and proustite, both silver-bearing minerals with striking red colors. While Pyrargyrite(deep red color) is silver antimony sulfide (Ag₃ SbS₃) and Proustite (Scarlet red color) is Silver arsenic sulfide (Ag₃ AsS₃). Both crystallize in the trigonal system and possess a Mohr’s hardness of 2.5 and specific gravity of 5.82.. Lunar caustic: Another name for silver nitrate (AgNO₃). An inorganic compound containing silver. Has antiseptic properties. Used in various medical applications, including the treatment of warts and as a cauterizing agent.

Explanation

Option (d) is correct: Cyclonite is another name for RDX (Research Department Explosive or Royal Demolition Explosive), which is a powerful military-grade explosive. It is widely used in military applications and mining operations due to its high detonation velocity and stability. Options (a), (b) and (c) are incorrect:

Cyanohydrin is a type of organic compound used in the synthesis of plastics and pharmaceuticals, not an explosive. Dextran is a complex sugar used in medical applications like blood volume expanders. Cyclohexane is a hydrocarbon commonly used as a solvent or in chemical synthesis, not an explosive.

Explanation

In pitcher plants (Nepenthes) the leaf is modified into a pitcher-shaped structure that traps and digests insects. This adaptation helps the plant supplement its nutrient intake in poor soil conditions, such as those found in bogs or marshes. Pitcher plants are carnivorous in nature.The rim of the pitcher has nectar glands or patterns that attract insects. Once inside the insect faces slippery walls or downward-facing hairs that trap it. It falls into digestive fluid at the bottom where enzymes break it down. The plant absorbs the nutrients and thrives in nutrient-poorhabitats like bogs.