Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Statement 1 is correct: DVD stands for "Digital Versatile Disk" or "Digital Video Disc". It is a type of digital optical disc storage that can hold any kind of digital data but is frequently used to store pictures, audio, and video in standard definition. Blu-ray Disc is a digital disc storage format similar to CD and DVD, that is designed to record and play a large amount of data with high-definition quality.

Statement 2 is correct: Blu-ray Disc media include these features: 50GB capacity - Each disc can hold more than 10 standard DVDs.

Statement 3 is incorrect: The size of the Blu-ray disc is 120 millimetres in diameter with 1.2 millimetres thickness, which is the same as the size of a CD and DVD.

Explanation

The tissue just beneath the bark called the phloem layer is in charge of moving food produced by photosynthesis from the leaves to the roots. This process is called girdling, and it is fatal to trees because it disrupts the transport of nutrients. Without this nourishment, the roots eventually perish and stop supplying the leaves with water and nutrients. Later, the leaves wither. Because its roots are starved of vitality, a tree that has had its bark removed in a circular pattern all around near its base gradually dries up and dies.

Explanation

Statement 1 is incorrect: The presence of ions, and not ozone, in the Ionosphere is responsible for radio communication. Ozone is primarily present in the Stratosphere and not in the Ionosphere.

Statement 2 is incorrect: They have frequencies from 300 GHz to as low as 3 kHz and corresponding wavelengths from 1 millimetre to 100 kilometres. They have a long range of wavelengths, so they can have very small wavelengths as well.

Explanation

Bt Brinjal is the first Genetically Modified food crop in India that has reached the approval stage for commercialization. Bt Brinjal is a genetically modified (GM) crop created by inserting Cry1Ac gene from the soil bacterium Bacillus thuringiensis into Brinjal. Brinjal plants now have resistance to lepidopteran pests such the Brinjal Fruit and Shoot Borer (Leucinodes orbonalis) and Fruit Borer as a result of the gene’s insertion (Helicoverpa armigera).

Explanation

The carbon cycle is a natural process that involves the movement of carbon between the atmosphere, oceans, soil, rocks, and living organisms. Respiration, decay of organic matter, volcanic action, fossil fuel combustion, deforestation, ocean-atmosphere exchange adds carbon to the cycle. All living organisms (plants, animals, and microorganisms) respire and breaking down glucose and oxygen to release energy, CO₂, and water. This process adds carbon dioxide to the atmosphere. When dead plants, animals, and other organic materials decompose microbes break them down. During decomposition CO₂ and methane (CH₄) are released into the atmosphere. Volcanic eruptions release stored carbon dioxide from the Earth’s mantle into the atmosphere. This is a natural source of CO₂ emissions. During photosynthesis plants, algae, and some bacteria absorb CO₂ from the atmosphere and use sunlight to convert it into glucose and oxygen. This process removes carbon dioxide from the atmosphere rather than adding it.

Explanation

CyberKnife is an advanced radiosurgery technology that allows real-time tracking and adjustment of radiation beams, ensuring precise targeting of tumors while minimizing damage to surrounding healthy tissues. These features make CyberKnife highly effective for treating tumors in sensitive areas such as the brain, spine, and lungs. Options (a), (b) and (c) are correct: CyberKnife is a non-invasive robotic radiosurgery system used to treat cancerous and non-cancerous tumors. It is a robotic image-guided system, capable of delivering extremely precise doses of radiation with sub-millimeter accuracy.

Option (d) is incorrect: CyberKnife is not designed to map the spread of tumors in the body. Its role is strictly limited to treating targeted tumor regions. Imaging techniques such as PET scans, CT scans, and MRIs are used to identify and map tumor spread, whereas CyberKnife focuses solely on delivering radiation therapy with exceptional precision.

Explanation

Golden rice is a genetically modified variety of rice specifically engineered to address vitamin A deficiency. The grains of Golden rice are biofortified with beta-carotene, a precursor of vitamin A (pro-vitamin A). When consumed, beta-carotene is converted into vitamin A in the human body, making golden rice an important dietary intervention to combat vitamin A deficiency, particularly in developing countries where this deficiency is prevalent and can lead to serious health issues like blindness.

Explanation

The 2.4 GHz and 2.5 GHz ISM band (Industrial, Scientific, and Medical) is a part of the radio frequency spectrum commonly used for short-range communication technologies. This range is globally available for unlicensed use, making it ideal for a variety of wireless communication applications. Bluetooth devices, cordless phones, microwave ovens, Wi-Fi baby monitors, wireless cameras, and RFID systems operate in the 2.4 to 2.5 GHz range of the radio frequency band. While it allows a variety of devices to operate within it, managing interference is a key challenge in environments with multiple devices using the same frequency. This range is commonly used due to its balance between range and data capacity, making it suitable for short-range communication and other applications.

Explanation

LASIK is primarily used to treat refractive errors such as nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. LASIK uses a laser to reshape the cornea, allowing light entering the eye to be properly focused onto the retina, improving vision. The goal of LASIK is to correct refractive errors and thereby reduce or eliminate the need for corrective eyewear like glasses or contact lenses. LASIK is typically not recommended for individuals under the age of 18 because their eyes may still be changing. Additionally, people over the age of 40 may not be ideal candidates due to presbyopia, a condition that affects near vision.

Explanation

Option (c) is correct: DSL (Digital Subscriber Line) is a wired broadband technology that uses telephone lines to transmit digital data. It is used for high-speed internet connections, but it is not a wireless technology. It does NOT belong to the GSM (Global System for Mobile Communication). DSL is a wired broadband technology that provides internet access over telephone lines and is unrelated to mobile networks. Options (a), (b) and (d) are incorrect:

EDGE (Enhanced Data Rates for GSM Evolution) belongs to the GSM family. It is an enhancement of GPRS (General Packet Radio Service) and is considered part of 2.5G and 2.75G networks within the GSM framework. LTE (Long-Term Evolution) belongs to the GSM family. LTE is a 4G technology that evolved from GSM and UMTS (Universal Mobile Telecommunications System). It provides high-speed wireless communication but is not strictly GSM-based; however, it is considered part of the evolutionary path of GSM networks.