Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Rare earth elements (REEs) are a group of 17 chemically similar metallic elements that are known for their high luster, high density, and unique magnetic, phosphorescent, and catalytic properties.

Statement 1 is correct: Rare earth elements such as europium, terbium, and yttrium are crucial for producing the bright, vivid colors in modern flat screens and monitors.

Statement 2 is correct: Many rare earth elements, like europium and terbium, have phosphorescent or luminescent properties, meaning they can absorb energy and emit light, which is used in various applications including displays.

Explanation

Microgravity research refers to scientific studies conducted in environments where the force of gravity is extremely low, causing objects and people to appear weightless. In such conditions, often found in space or simulated on Earth, researchers can observe how physical, chemical, and biological systems behave differently than they do under normal gravity. Options 1, 2, and 3 are correct:

Axiom-4 is a private mission to the ISS that will conduct around 60 scientific studies, including several led by ISRO, with a strong focus on microgravity research across various disciplines such as biology, medicine, and materials science. ISRO and ESA are collaborating on microgravity research experiments specifically for Axiom-4. SpaDeX is an ISRO technology demonstrator for in-space docking. The mission uses the PSLV’s fourth stage (POEM-4) to carry 24 payloads from academia and startups, which will utilize the microgravity environment in orbit for scientific experiments. The mission explicitly provides opportunities for in-orbit microgravity experiments for extended durations. Gaganyaan is India’s first human spaceflight mission, led by ISRO. Scheduled to send Indian astronauts into low Earth orbit, it aims to demonstrate indigenous capability in crewed space missions. Gaganyaan will also facilitate scientific research in microgravity, marking a significant milestone in India’s space exploration journey.

Explanation

Pair 1 is correctly matched: Dornier -228 is known for their versatility, they are equipped for a range of missions, including maritime patrol, surveillance, pollution control, search and rescue, and medical evacuation.

Pair 2 is not correctly matched: The Ilyushin Il-76 is a strategic/heavy military transport aircraft, not a supersonic combat aircraft. HAL Tejas, MiG-21, Sukhoi Su-30MKI and Dassault Rafale are examples of supersonic combat aircraft.

Pair 3 is correctly matched: The C-17 Globemaster III is a large military transport aircraft used for airlift and cargo missions. The Indian Air Force (IAF) has received its third Boeing C-17 Globemaster III, a large, versatile military transport aircraft capable of carrying heavy, oversize loads long distances and landing on rough and unprepared surfaces.

Explanation

The membrane bioreactor (MBR) has emerged as an efficient compact technology for municipal and industrial wastewater treatment. These systems have the advantage of combining a suspended growth biological reactor with solids removal via filtration. Membranes in MBR systems are designed to function efficiently in compact spaces while effectively removing contaminants like nitrogen, phosphorus, bacteria, biochemical oxygen demand (BOD), and total suspended solids (TSS). The filtration process supports higher biomass concentrations, enabling the use of smaller bioreactors. The effluent from MBRs contains low concentrations of bacteria, total suspended solids (TSS), and biochemical oxygen demand (BOD). This facilitates high-level disinfection. Effluents are readily discharged to surface streams or can be sold for reuse, such as irrigation.

Explanation

Nitric oxide is a naturally synthesized molecule in the human body that plays a crucial role in vasodilation, which is the widening of blood vessels. It is produced by endothelial cells lining the blood vessels through the action of the enzyme nitric oxide synthase (NOS) on L-arginine. Nitric oxide diffuses into the smooth muscle cells of blood vessels. It activates an enzyme called guanylate cyclase, which increases the production of cyclic guanosine monophosphate (cGMP). cGMP causes the relaxation of smooth muscles, leading to the widening of blood vessels (vasodilation). By relaxing the smooth muscles of blood vessels, nitric oxide increases blood flow and helps regulate blood pressure. It also has important functions in immune response and neurotransmission.

Explanation

Radar (Radio Detection And Ranging) is an electromagnetic sensor used for detecting, locating, tracking, and recognising objects of various kinds at considerable distances. It operates by transmitting electromagnetic energy toward objects, commonly referred to as targets, and observing the echoes returned from them. The targets may be aircraft, ships, spacecraft, automotive vehicles, astronomical bodies, or even birds, insects, and rain. Besides determining the presence, location, and velocity of such objects, radar can sometimes obtain their size and shape as well.

Statement 1 is incorrect: Radar technology is being used in the fight against narcotics, but they are being used for interdiction of suspicious flights/aircraft in countries like Guatemala, Brazil and Bolivia and not directly in the identification of narcotics on passengers or in the aircraft.

Statement 2 is correct: Radars, especially Doppler weather radars, are widely used to track precipitation, storm patterns, and weather conditions.

Statement 3 is correct: Radars, such as avian radars, are used to monitor the movement of birds and other animals, especially for ecological studies and aviation safety.

Explanation

The Metaverse refers to an interoperable network of 3D virtual worlds where users can interact, own virtual assets, and engage in various digital activities. It allows millions of users to access and participate simultaneously, often using technologies like virtual reality (VR), augmented reality (AR), and blockchain. Prominent Applications of the Metaverse:

Gaming & Social Interaction - Immersive experiences on platforms like Horizon Worlds and Roblox. Education & Training - VR based learning, medical simulations, and corporate training. Retail & E-Commerce - Virtual stores by brands like Nike and Gucci. Healthcare - VR therapy, remote surgeries, and medical training. Real Estate & Architecture - 3D virtual property tours and design modeling. Work & Collaboration - Virtual offices and meetings (e.g., Microsoft Mesh). Entertainment & Events - Virtual concerts, movies, and live shows. Finance & Virtual Economy - NFTs, digital assets, and blockchain-based transactions. Industry & Manufacturing - Digital twins and AR for production efficiency. Tourism & Exploration - Virtual travel experiences of historical and cultural sites.

Option (c) is correct: "Metaverse" is the most appropriate because it directly encompasses all three of these key features: interconnected 3D virtual worlds, massive concurrent user access, and crucially, the ability to own and manage virtual property. Examples:

Decentraland: Users can interact, purchase virtual land, develop businesses, and trade NFTs. The Sandbox: A virtual economy where users create, own, and monetize digital assets. Options (a), (b) and (d) are incorrect:

Big Data Analytics refers to the process of analyzing large and complex datasets to uncover patterns, trends, and insights. It utilizes advanced techniques such as machine learning, artificial intelligence (AI), and statistical analysis to extract meaningful information. Examples include Netflix’s recommendation system, Google search algorithms, and customer behavior analysis in e-commerce. Overall, this explanation does not resemble the phrase used in the question statement. Cryptography involves techniques for secure communication and data protection through encryption and decryption methods. It ensures confidentiality, integrity, authentication, and non-repudiation in digital transactions. Cryptographic methods are essential in cybersecurity, digital signatures, blockchain technology, and secure online communications. They are commonly used in applications such as SSL encryption for websites, Bitcoin transactions, and end-to-end encrypted messaging apps like WhatsApp. Virtual Matrix is not a widely recognized term in the domain of 3D interconnected virtual worlds. The word "Matrix" is sometimes associated with simulated realities, as seen in science fiction, such as The Matrix movie. However, it does not specifically refer to an interoperable digital ecosystem like the Metaverse. If used in a technical sense, it might refer to a virtual computing environment or a data organization framework, but it does not describe a user-driven virtual space where individuals can exert property rights over digital assets.

Explanation

Hydrogels are three-dimensional polymer networks that can absorb and retain large amounts of water while preserving their structure. With their biocompatibility, flexibility, and customizable properties, they are widely utilized across various applications.

Option 1 is correct: Hydrogels have a porous, water-attracting structure that allows them to expand and contract in response to stimuli. This makes them ideal for controlled drug delivery, ensuring precise and sustained release in liquid environments.

Option 2 is incorrect: Hydrogels are not commonly used in mobile air-conditioning systems. Air-conditioning relies on compressors, refrigerants, and heat exchangers, and though materials with moisture retention might play a minor auxiliary role (like evaporative cooling pads), hydrogels are not a standard component in these systems.

Option 3 is incorrect: Hydrogels do not serve as specific base materials or additives in conventional industrial lubricants. Industrial lubricants typically rely on oils, greases, and synthetic compounds designed for reducing friction and wear. Hydrogels are not chemically or mechanically suited for this purpose. Note: UPSC has given Option(a) as an official answer.

Explanation

Stars are classified based on their size, mass, and brightness into categories such as giant stars and dwarf stars. Giant stars are massive, highly luminous stars that burn They are often in the later stages of stellar evolution. Dwarf stars, on the other hand, are smaller, less luminous, Red dwarfs, the most common type, can burn for trillions of years, while white dwarfs are the remnants of low to medium-mass stars after they exhaust their nuclear fuel.

Statement I is incorrect: Giant stars have much shorter lifespans than dwarf stars. Giant stars burn fuel quickly because of their high mass and energy, while red dwarf stars use fuel slowly, allowing them to last billions or even trillions of years.

Statement II is correct: Giant stars have much higher core temperatures and pressures, leading to faster nuclear fusion rates compared to dwarf stars. This high rate of fusion results in a shorter lifespan.

Explanation

Fifth-generation fighter aircraft typically have features like stealth, advanced avionics, sensor fusion, and supercruise capability. Examples include the F-35 Lightning II (USA), F-22 Raptor (USA), Su-57 (Russia), and J-20 (China). They differ from fourth-generation aircraft primarily in their stealth features. Fifth-generation aircraft have a low electromagnetic signature, which makes it difficult for enemy radar to detect them. At the same time, fifth-generation aircraft have powerful sensors and new weapons, so they are able to register the signature of enemy aircraft and take them out.

Option 1 is incorrect: Rafale is a 4.5-generation multirole fighter developed by Dassault Aviation (France). It features advanced avionics, stealth enhancements, and superior maneuverability but lacks full stealth and sensor fusion, which are key traits of fifth-generation aircraft.

Option 2 is incorrect: MiG-29 is a fourth-generation fighter developed by Russia, primarily designed for air superiority with high agility but lacks stealth technology.

Option 3 is incorrect: Tejas MK-1 is an indigenously developed fourth-generation light combat aircraft (LCA) by India with modern avionics but does not meet fifth-generation requirements.