Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Option (b) is correct: The major challenge in developing a malaria vaccine is that humans do not achieve complete immunity through natural infection. Partial immunity can develop after repeated exposure but it is not sufficient to prevent reinfection as the immune system fails to completely clear the parasite. The malaria parasite’s high mutation rate enables it to evade the immune system, further complicating efforts to develop an effective vaccine.

Option (a) is incorrect: Although malaria is caused by various Plasmodium species (e.g., P. falciparum, P. vivax) but this diversity is not the primary obstacle to vaccine development. Vaccines can target shared stages of the parasite’s lifecycle, allowing scientists to address multiple species. While species variation presents a challenge, it is not the main barrier in creating an effective vaccine against malaria.

Option (c) is incorrect: Vaccines have been successfully developed for a wide range of pathogens, including viruses, bacteria, and parasites like malaria.

Option (d) is incorrect: Though humans are the intermediate host for the Plasmodium parasite, they are also crucial in the parasite’s lifecycle. The mosquito is the definitive host, where the parasite undergoes sexual reproduction. In humans the parasite undergoes asexual reproduction inside the liver and red blood cells, making humans essential in the lifecycle.

Explanation

Hepatitis B is a viral infection that primarily affects the liver and can lead to chronic disease. HIV is a virus that attacks the immune system, weakening the body’s ability to fight infections.

Statement 1 is correct: Hepatitis B transmission occurs through contact with infected blood, semen, or other body fluids. It’s 50 to 100 times more contagious than HIV because it can survive longer outside the body and can be transmitted with a smaller amount of the virus. HIV (Human Immunodeficiency Virus) needs a higher viral load and specific conditions to spread.

Statement 2 is correct: The Hepatitis B virus attacks and damages the liver, causing inflammation and scarring (called cirrhosis). This chronic inflammation weakens the liver and makes it more susceptible to liver cancer. Liver cancer specifically hepatocellular carcinoma (HCC) is strongly associated with chronic HBV infection. People with chronic Hepatitis B infection have a much higher risk of developing HCC compared to those who do not have the infection.

Explanation

WiMAX (WIMAX forum was formed in June 2001 to promote conformity and interoperability) is a communication technology that provides high-speed wireless broadband internet access. It is designed to offer both fixed and mobile broadband services over long distances, often as a replacement or supplement to traditional wired broadband technologies like digital subscriber line (DSL) or cable. Broadband Internet Access, Wireless Backhaul (for wireless link between a cellular base station and the core network) and Mobile Broadband etc. are based on WiMAX technology. It provides high-speed internet access, bridging the connectivity gap for both urban and rural areas, especially in the last-mile segment.

Explanation

The Shourya is a canisterised missile system that can be easily handled, transported and stored within the canister for longer shelf-life. The high manoeuvrability of the missile makes it less vulnerable to available anti-missile defence systems.

Statement 1 is incorrect: The Can carry a payload of 200 to 1000 kg.Propellant - Solid fuel is a hypersonic surface-to-surface tactical missile. It is known to travel at speeds of up to Mach 7.5, which is slightly less than Mach 8.

Statement 2 is incorrect: The range of the Shourya missile is approximately 750-1900 km, depending on its payload, but its operational range typically does not exceed 1600 km in standard configurations.

Explanation

Statement 1 is incorrect: INS Sindhughosh is not an aircraft carrier. It is a diesel-electric submarine of the Sindhughosh class, which is based on the Russian Kilo-class submarines. It is used for anti-submarine warfare, reconnaissance, and intelligence gathering.

Statement 2 is incorrect: INS Viraat is not a submarine. It was an aircraft carrier and served as the flagship of the Indian Navy for many years. It played a significant role in enhancing India’s naval power before being decommissioned in 2017.

Explanation

Sub-atomic particles are particles that are smaller than an atom. They are the basic building blocks of atoms. They are primarily categorized into two groups: elementary particles which are indivisible, and composite particles which are combinations of elementary particles.

Option (b) is correct: In the year 2008, the organization that conducted a complex scientific experiment in which sub-atomic particles were accelerated to nearly the speed of light was the European Organization for Nuclear Research (CERN). CERN operates the Large Hadron Collider (LHC), where particles are accelerated to extremely high speeds to explore fundamental physics. The experiment helps in understanding the Standard Model of Particle Physics exploring dark matter and studying the properties of fundamental forces.

Explanation

Option (c) is correct: Night vision apparatus detects infrared waves emitted by objects as heat. Warmer objects emit more infrared radiation which is invisible to the human eye but can be captured and converted into a visible image by night vision devices. Infrared waves are electromagnetic waves with wavelengths longer than visible light but shorter than microwaves, typically used in thermal imaging, night vision, and remote sensing. Options (a) and (b) are incorrect: Microwaves are used in cooking and radar systems and radio waves are used for communication in broadcasting, mobile phones, and satellite transmissions.

Explanation

Ammonium chloride (NH₄Cl) is a primary component of the electrolyte paste used in dry cells. Zinc chloride (ZnCl₂) serves as the negative electrolyte, and it is often mixed with ammonium chloride in a paste to form the electrolyte for the dry cell. These components, along with a zinc anode and a carbon cathode, are commonly used in the construction of dry cells, which power small devices such as flashlights and radios.

Explanation

Option (d) is correct: Nitroglycerine is a highly explosive compound, commonly used in the production of dynamite. It is a liquid with high sensitivity to shock and heat, making it a powerful and widely used explosive in mining and demolition. Options (a), (b) and (c) are incorrect:

Phosphorus Trichloride is a chemical used in the manufacture of pesticides, not an explosive. Mercuric Oxide is an oxidizing agent used in batteries and chemical synthesis, not explosive. Graphite is a form of carbon used in lubricants and as an electrode material, not an explosive.

Explanation

Saffron spice is made from the stigma of the Crocus sativus flower, commonly known as the saffron crocus. The stigmas are handpicked, dried, and processed to produce saffron. Each flower has only three stigmas, making the harvesting process labor-intensive and contributing to saffron’s high value. The stigmas are highly prized for their distinctive flavor, aroma, and vibrant golden color.