UPSC 2002 Science and Technology Questions with Answers

Explanation

Stem cells are undifferentiated cells with the potential to develop into various specialized cell types, offering promise for regenerative medicine and disease treatment

Statement 1 and 2 are incorrect: The blastocyst stage of embryos is a common source of embryonic stem cells, but it is not the only source. Stem cells can also be derived from adult tissues (adult stem cells) and umbilical cord blood. As of current techniques, obtaining embryonic stem cells typically requires the destruction of the blastocyst. Alternative methods are being actively researched to derive stem cells without causing harm to the blastocyst.

Statement 3 is correct: Stem cells, such as embryonic stem cells have the ability to self-renew and regenerate themselves in vitro indefinitely under appropriate conditions. This property makes them valuable for research and therapeutic applications.

Statement 4 is correct: Indian research centers, such as the National Centre for Biological Sciences (NCBS) and the Indian Council of Medical Research (ICMR), have successfully created a few stem cell lines capable of differentiating into multiple tissue types.

Explanation

INSAT or the Indian National Satellite System is a series of multipurpose Geostationary satellites launched by ISRO to satisfy the telecommunications, broadcasting, meteorology, and search and rescue needs of India.

Statement 1 is correct: The INSAT-series of satellites were launched from foreign stations like Kourou in French Guiana or Kennedy Space Center in the USA.

Statement 2 is correct: The PSLV (Polar Satellite Launch Vehicle) was used to launch many of the IRS (Indian Remote Sensing) satellites, which are used for Earth observation.

Statement 3 is correct: India’s first cryogenic engine was used for the third stage of the GSLV (Geosynchronous Satellite Launch Vehicle) for the first time in the launch of GSLV-D3 in 2010.

Statement 4 is correct: GSAT-1, India’s first geostationary communication satellite, was launched in 2001, and its payloads were designed to provide digital broadcast and communication services, including internet services.

Explanation

A satellite is an object in space that orbits or circles around a bigger object. There are two kinds of satellites: natural (such as the moon orbiting the Earth) or artificial (such as the International Space Station orbiting the Earth). Almost every planet having at least one moon. Assertion (A) is true: Satellites are launched in the eastward direction to take advantage of the Earth’s rotational velocity, which gives the rocket an initial boost in speed. This helps the rocket reach the required escape velocity more efficiently. Reason (R) is false: While the Earth’s rotation does provide a velocity boost but it does not directly help the satellite attain escape velocity (the speed needed to break free from Earth’s gravity, approximately 11.2 km/s). Instead, the Earth’s rotation helps the satellite achieve orbital velocity (the speed needed to stay in orbit, approximately 7.8 km/s for low Earth orbit).

Explanation

Density is a measure of how much mass is packed into a given volume. Buoyancy is the tendency of an object to float in a fluid. An object floats if its density is less than the fluid’s density and sinks if its density is greater. If the densities are equal, the object remains neutrally buoyant, neither sinking nor floating. Assertion (A) is true: Iron is denser than water, so it sinks in water. However, mercury is denser than iron, so an iron ball will float on mercury. Reason (R) is false: Specific gravity is the ratio of the density of a substance to the density of a reference substance (usually water). Mercury is denser than iron, so its specific gravity is higher.

Explanation

The rate at which an object cools depends on its surface area-to-volume ratio and temperature difference with the surroundings. A higher surface area-to-volume ratio allows more heat to be dissipated into the surroundings, leading to faster cooling. The sphere has the largest surface area compared to the cube and circular plate. The larger the surface area, the more heat can be radiated or transferred to the surroundings, which leads to a faster cooling rate. The sphere cools faster than the circular plate and cube for the same radius. The more heat the sphere can radiate, the quicker it will reach room temperature compared to objects with smaller surface areas. Note: Here, we can ignore the impact of volume as the sphere, disc or cube all are hollow with negligible thickness.

Explanation

Statement 1 is incorrect: According to Rayleigh scattering, light with shorter wavelengths (e.g., blue light) is scattered more than light with longer wavelengths (e.g., red light).

Statement 2 is incorrect: The refractive index of water is approximately 1.33, so the speed of light in water is about 1/1.33 0.75° the speed in a vacuum.

Statement 3 is correct: Radio waves are a type of electromagnetic radiation generated when electrical charges oscillate in an antenna. These oscillations create alternating electric and magnetic fields that propagate as waves. This principle is the basis of wireless communication technologies like radio, TV, and mobile networks.

Statement 4 is correct: The Doppler effect is used in radar guns to measure the speed of moving vehicles by analyzing the frequency shift of reflected radio waves.

Explanation

A mirage is primarily caused by terrestrial heating and the refraction of light. Mirage causes deceptive appearance of a distant object or objects caused by light ray bending (refraction) in different density layers of air. Terrestrial Heating: The ground is intensely heated by the sun (such as a hot road or desert). This heats the air near the surface, making it less dense than the cooler air above. The temperature gradient creates a gradient in the refractive index of the air. Refraction of Light: Light from the sky or distant objects passes through the layers of air with varying temperatures and densities. The light bends (refracts) as it moves from cooler, denser air to hotter, less dense air. This bending creates the illusion of water or a mirrored surface on the ground.

Explanation

Assertion (A) is true: Synthetic detergents, unlike soap, work efficiently in hard water because they do not form insoluble scum with calcium and magnesium ions, which are present in hard water. This enables better lathering. Reason (R) is true: Synthetic detergents are mainly non-ionic or anionic, allowing them to form soluble complexes with calcium and magnesium ions, preventing scum formation. Unlike soap, which forms insoluble salts, these detergents continue to lather in hard water. Reason (R) correctly explains Assertion (A) because synthetic detergents form soluble complexes with calcium and magnesium, preventing scum and aiding lathering in hard water. Direction: The following item consists of two statements. One labeled as the ‘Assertion (A)’ and the other as "Reason (R)". You have to answer this item using the code given below:

Explanation

Dichogamy refers to the condition in a bisexual flower where the male (androecium) and female (gynoecium) reproductive organs mature at different times to prevent self-pollination. This ensures cross-pollination between different plants or flowers which increases genetic diversity.

Explanation

Stem cutting is a common asexual propagation method where a section of the stem, with at least one node and some leaves is cut from a parent plant and rooted to grow a new, genetically identical plant. This method helps maintain desirable plant traits. Bougainvillea, carnations, grapes, and cocoa can all be propagated by stem cuttings. Bougainvillea is propagated using hardwood(during the dormant season) or softwood (during spring/summer from young growth) cuttings depending on the season. Carnations: Stem cuttings taken from side shoots in spring/ summer. Must have two nodes and leaves for successful propagation. Grapes: Dormant hardwood cuttings taken during winter with 3 nodes. Ideal for maintaining grapevine traits. Cocoa: Propagated using young, tender stem cuttings during the rainy season. Cuttings should have at least two nodes and leaves.