Physics & Materials Science

* Statement 1: Incorrect. RTGs (Radioisotope Thermoelectric Generators) are not miniature fission reactors. Fission reactors use nuclear fission, a process of splitting atoms to release a tremendous amount of energy. RTGs, on the other hand, utilize the natural radioactive decay of isotopes to generate heat, which is then converted to electricity through a process called thermoelectricity. * Statement 2: Correct. RTGs are indeed a reliable power source for spacecraft, especially those venturing far from the sun where solar panels become ineffective. They provide consistent, low-level electric power for extended periods, making them ideal for probes, satellites, and rovers in deep space. * Statement 3: Correct. Plutonium-238 is a common isotope used in RTGs due to its long half-life (the time it takes for half of the material to decay) and its ability to generate a steady heat output from its decay process. While it can be a byproduct of weapons development, there are also alternative ways to produce Plutonium-238 specifically for peaceful applications like RTGs.

* Ilmenite (FeTiO3) and Rutile (TiO2) are both minerals that contain high concentrations of titanium.  * Titanium is a strong and lightweight metal known for its excellent corrosion resistance and high strength-to-weight ratio. It is widely used in various industries, including aerospace, automotive, medical, and construction.  * In India, certain coastal tracts are known for their significant ilmenite and rutile deposits. Hence these minerals are also called beach sand minerals. These minerals are commonly found in beach sand deposits and are extracted through beach sand mining operations. The extracted ilmenite and rutile are processed to obtain titanium dioxide (TiO2), which is then further refined to produce metallic titanium.  * Beach sand is rich in seven heavy minerals—ilmenite, leucoxene, rutile, zircon, sillimanite, garnet and monazite.

* Statement I is Correct : India has domestic uranium reserves, but they are not enough to meet the country's nuclear power generation needs. Additionally, some nuclear reactors in India use imported uranium. Coal remains the dominant source of electricity production in India, although its share is gradually decreasing.  * The major uranium deposits of the country occur in geological basins of the Singhbhum shear zone (Jharkhand), Cuddapah basin (Andhra Pradesh and Telangana), Mahadek basin (Meghalaya), Delhi Supergroup of rocks (Rajasthan) and Bhima basin (Karnataka). * Statement II is Incorrect : Nuclear power plants can utilise uranium enriched to varying degrees. India primarily uses Pressurised Heavy Water Reactors (PHWRs) that can function efficiently with low-enriched uranium (around 2-5% enrichment).

* Neither of the statements about ballistic missiles and cruise missiles is accurate. * Ballistic missiles: These are rocket-powered weapons that follow a high, arcing trajectory after a brief powered ascent. They travel at supersonic speeds throughout most of their flight due to inertia. * Cruise missiles: These are jet-propelled weapons that fly at relatively low altitudes and can manoeuvre throughout their flight path. They can be subsonic, supersonic, or hypersonic depending on the design. * Agni-V: This is a long-range intercontinental ballistic missile (ICBM) developed by India. It is not a medium-range cruise missile. * BrahMos: This is a supersonic cruise missile jointly developed by India and Russia. It is not a solid-fueled ICBM. BrahMos uses a ramjet engine for sustained supersonic flight after a booster rocket launch.

* Carbon fibres are highly valued for their unique properties like strength, lightness, and stiffness. They are widely used in the manufacturing of various components in automobiles and aircraft to reduce weight and improve performance.  * Carbon Fiber Recycling: While traditional carbon fibre recycling methods were limited, advancements are being made in this field. Here are some possibilities  1. Mechanical recycling - This process breaks down carbon fibres into smaller pieces for use in applications where their original form is not necessary.  2. Chemical recycling -This method dissolves the resin holding the fibres together, potentially allowing the extraction of reusable carbon fibres.  3. Thermal recycling - High temperatures are used to convert the resin into usable materials while recovering the carbon fibres.  * These recycling technologies are still evolving, but they offer a more sustainable approach to using carbon fibres. Hence, statement 2 is incorrect.

Monazite is a brown crystalline mineral consisting of cerium, lanthanum, other rare earth elements, and thorium. Monazite usually occurs in small, isolated crystals or grains that are resistant to weathering and become concentrated in soils. Statements 1 and 2 are correct. Monazite is a major source of rare earths and thorium. It yields several rare-earth elements, such as neodymium and praseodymium. Both of these are in demand internationally for making high-performance rare-earth magnets (components of power wind turbines, electric vehicles and robotics) Statement 3 is incorrect. Though monazite is found in most coastal areas of India. It is questionable to be found along the entire coast. The main mines are found along the coasts of southern India in Kerala, Tamil Nadu and in Orissa. Statement 4 is correct. Export of monazite without a license from AERB is a violation of the Atomic Energy (Radiation Protection) Rules 2004. Indian Rare Earths Limited (IREL), a wholly owned Public Sector Undertaking of the Government of India (GOI) under DAE, is the only entity that has been permitted to produce and process monazite and handle it for domestic use as well as for export.

Statement 1 is incorrect: Nanoparticles can exist in nature (natural nanoparticles). Volcanic eruptions, forest fires, and natural weathering processes can all create nanoparticles. Statement 2 is correct: Some cosmetics incorporate nanoparticles of ingredients like zinc oxide or titanium dioxide for sun protection or other purposes. Statement 3 is also correct: The safety of nanoparticles in consumer products is a complex issue and a growing area of research. Some nanoparticles might pose potential health or environmental risks depending on their specific properties and how they interact with the body or the environment.

Water molecules are polar, meaning they have a positive charge on one end (the hydrogen atoms) and a negative charge on the other end (the oxygen atom). This polarity allows water molecules to attract and interact with other polar or charged molecules, facilitating the dissolution of a wide range of substances in water. Therefore, option (a) is correct.

Statement 1 is correct. Sodium lamps emit light in a 360-degree pattern, while LED lamps are directional. Statement 2 is incorrect. LED lamps generally have a longer lifespan compared to sodium lamps. Statement 3 is correct. Sodium lamps emit monochromatic light, whereas LED lamps offer a wider spectrum of visible light, providing significant colour advantages in street lighting.

Statement 1 is correct: The size of the hole in the lid regulates the amount of steam released. A larger hole permits more steam to escape, leading to reduced pressure and subsequently affecting the temperature. Statement 2 is incorrect: Boiling water can never exceed 100 degrees Celsius, regardless of the intensity of the flame beneath the pot. However, within a pressure cooker, the temperature can elevate to as high as 121 degrees Celsius. The heightened cooking temperature serves to decrease the cooking duration rather than the temperature itself. Statement 3 is correct: If the weight is heavier, it will require higher pressure to lift it, resulting in higher pressure inside the cooker before excess steam can escape. Higher pressure leads to a higher boiling point for the water inside the cooker, which in turn increases the cooking temperature. Conversely, if the weight is lighter, it results in a lower pressure inside the cooker and a lower boiling point for the water, leading to a lower cooking temperature.