Day-773 | Daily MCQs | UPSC Prelims | SCIENCE AND TECHNOLOGY

Answer: C
Explanation
Osteoarthritis is a degenerative joint condition. It causes pain, swelling and stiffness, affecting a person’s ability to move freely. Many factors can contribute to developing osteoarthritis. Some include a history of joint injury or overuse, older age and being overweight. It affects women more than men. By 2050, nearly one billion people globally are projected to be living with osteoarthritis, according to new research published in The Lancet Rheumatology journal.
Statement 1 is correct: Osteoarthritis is a degenerative joint condition. It is chronic and often progressive, so changes happen gradually over time.
Statement 2 is correct: Obesity or abnormally high Body Mass Index reduces the flexibility of joints and muscles.
Statement 3 is correct: It generally affects limbs and associated joints like knees and hands. Because of reduced movement, muscles often lose strength and people become less able to perform physical activities.

Answer: D
Explanation:
A humanoid robot is a robot resembling a human body in shape. It may be designed for functional purposes, such as interacting with human tools and environments. It may also be designed for experimental purposes, such as the study of bipedal locomotion, muscle movements, depth perception etc.

Answer: B
Explanation:
Some people who have been infected with the virus that causes COVID-19 can experience long-term effects from their infection, known as Long COVID or Post-COVID Conditions (PCC).
• Statement 1 is correct: As per WHO, Long COVID is defined as signs, symptoms, and conditions that continue or develop 3 months after acute COVID-19 infection.
• Statement 2 is correct: Common symptoms of long COVID include fatigue, shortness of breath and cognitive dysfunction. However, over 200 different symptoms have been reported that can have an impact on everyday functioning.
• Statement 3 is incorrect: Post COVID-19 Condition or Long COVID can affect anyone exposed to SARS-CoV-2, regardless of age or severity of original symptoms.

Answer: C
Explanation
A shock wave is a type of propagating disturbance that moves faster than the speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a medium but is characterized by an abrupt change in pressure, temperature, and density of the medium.

Answer: C
Explanation:
• Statement 1 is correct: Transgenic plants are plants that have been genetically engineered, a breeding approach that uses Recombinant DNA techniques to create plants with new characteristics. They are identified as a class of genetically modified organisms (GMOs). It is done via gene-splicing technique. Gene splicing is a technique of cutting the desired portion of gene using gene editing tools from other organisms and then recombining it to the original plant tissue which has been cultured. This creates a new plant with an altogether different trait. For example- Bt Cotton has been created by adding Bt toxin gene from a class of bacteria known as Bacillus thuringiensis (or Bt), which creates insect resistance without the need for insecticides.
• Statement 2 is correct: A hybrid plant is the result of cross pollinating two different plant varieties and growing the seed the mix produces. The plant that grows from that seed combination is called a hybrid. It is a natural method of gene transfer from parents to off springs but using two different plants from the same genus but different species. For example, Pomato is a hybrid plant produced by grafting together a tomato plant and a potato plant. Both have the same genus called Solanum. But species are different.

Answer: B
Explanation:
Sexually transmitted diseases (STDs), or sexually transmitted infections (STIs), are infections that are passed from one person to another through sexual contact. Some STDs can be passed from a pregnant person to the baby, either during pregnancy or when giving birth. Other ways that STDs may be spread include during breastfeeding, through blood transfusions, or by sharing needles.
Some of the common STDs are:
o Chlamydia
o Genital herpes
o Gonorrhea
o HIV
o HPV
o Pubic lice
o Syphilis
o Trichomoniasis
• Statement 1 is correct: Antibiotics can treat STDs caused by bacteria or parasites. Three bacterial (chlamydia, gonorrhea, and syphilis) and a parasitic STD (trichomoniasis) are generally curable with existing single-dose regimens of antibiotics.
• Statement 2 is correct: STDs caused by a virus cannot be cured. STDs caused by viruses include herpes and HIV. The most effective medications available are antivirals that can modulate the course of the disease, though they cannot cure the disease.
• Statement 3 is incorrect: Gonorrhea is a sexually transmitted disease caused by infection with the Neisseria gonorrhoeae bacterium. It infects the mucous membranes of the reproductive tract, including the cervix, uterus, and fallopian tubes in women, and the urethra in women and men.

Answer: B
Explanation:
• Statement 1 is correct: Many of the world’s animals can regrow lost teeth. Most of those animals are fish or reptiles. But in human beings, teeth can regrow only during childhood. Adult human beings cannot regrow missing or lost teeth. Options such as dental implants, bridges, and dentures can act as artificial replacements for lost teeth. This is because the stem cell which is associated with dental regeneration is lost along with the second teeth. Second teeth are the regrowth of new set of teeth after first teeth fall off in childhood.
• Statement 2 is correct but is not the correct explanation of statement 1: Enamel is the hardest substance in the human body. But it has nothing to do with the inability to regenerate lost teeth.
About Tooth Enamel
Tooth enamel is thin-layered, translucent, tough shell covering the tooth crown and the hardest tissue in humans. Enamel is made up of hydroxyapatite. It protects the teeth from decaying, erosion happening due to the use of teeth such as chewing, biting, etc. Damage caused to enamel tends to erosion and cavity forming in the tooth. Brush, floss, and rinse are key to keeping enamel healthy.

Answer: B
A mental disorder is characterized by a clinically significant disturbance in an individual’s cognition, emotional regulation, or behaviour. It is usually associated with distress or impairment in important areas of functioning.
• Pair 1 is incorrect: Depression is a type of mood disorder. It is associated with the feeling of sadness, irritation and emptiness or a loss of pleasure/interest in activities for most of the day. Excessive fear and worry are symptoms of anxiety disorder.
• Pair 2 is correct: Schizophrenia is a psychotic disorder which is characterized by significant impairments in perception and changes in behaviour. Symptoms may include persistent delusions, hallucinations, disorganized thinking, highly disorganized behaviour, or extreme agitation.
• Pair 3 is correct: Kleptomania is an example of impulse control and addiction disorder. Kleptomania involves repeatedly being unable to resist urges to steal items that one generally doesn’t need. Often the items stolen have little value.

Answer: C
Explanation:
Quantum dot LED (or QLED) and Organic LED (or OLED) are two of the most popular display technologies in the premium display segment. But there is a difference in technology between the two.
• Statement 1 is correct: QLED displays use quantum dots which produce brighter colours when excited by a backlight. However, the display lacks the colour accuracy produced by OLED.
• Statement 2 is correct: OLED produces better contrasts and can achieve true black. Because each pixel produces its own light, black is possible by just turning off the pixel — something that’s not possible with any backlit panel. Those deep blacks improve contrast and produce a more film-like viewing experience. Those individual pixels also can produce amazingly accurate colors.

Answer: A
Explanation:
The sun’s atmosphere is made up of several layers, mainly the photosphere, the chromosphere, and the corona. It’s in these outer layers that the sun’s energy, which has bubbled up from the sun’s interior layers over the course of a million years, is detected as sunlight. The outermost layer is corona. Chromosphere is a sandwich layer between corona and photosphere. The photosphere is the innermost layer out of the three.
• Pair 1 is incorrect: The chromosphere plays a role in conducting heat from the interior of the sun to its outermost layer, the corona.
• Pair 2 is incorrect: The photosphere is the innermost layer of the sun’s atmosphere — the innermost layer we can observe directly. The term photosphere means “sphere of light” and is the layer where most of the sun’s energy is emitted. It is thus, the visible surface of the sun.
• Pair 3 is correct: Corona is the outermost layer of the Sun’s atmosphere. The solar wind is caused by the outward expansion of plasma in the Sun’s corona. The corona is usually hidden by the bright light of the Sun’s surface. That makes it difficult to see without using special instruments. However, the corona can be seen during a total solar eclipse.

Answer: A
Explanation:
About flight recorder
A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. There are two types of flight recording devices: the flight data recorder (FDR) preserves the recent history of the flight through the recording of dozens of parameters collected several times per second; the cockpit voice recorder (CVR) preserves the recent history of the sounds in the cockpit, including the conversation of the pilots. The two devices may be combined into a single unit. Together, the FDR and CVR objectively document the aircraft’s flight history, which may assist in any later investigation.
• Statement 1 is correct: The device is often referred to colloquially as a “black box”.
• Statement 2 is incorrect: They are required to be painted BRIGHT ORANGE, to aid in their recovery after accidents. Typically, an airplane has two black boxes located at the front and rear of the aircraft.

Answer: B
Explanation
• States of matter are distinct physical phases in which matter can exist. However, they can change from one state to another by changing pressure and temperature.
• Solid, liquid, gas and plasma are 4 states of matter that occur naturally. Plasma is found in the ionosphere of the Earth’s atmosphere. Moreover, plasma is abundant in the Universe.
• Chiral Bose State is a quantum state at very low temperatures. This is only possible in laboratory and thus it is a man-made state of matter.
• A time crystal is an object whose parts move in a regular, repeating cycle, sustaining this constant change without burning any energy. This is a man-made state of matter. It is a kind of perpetual motion machine which defeats the laws of thermodynamics. A perpetual motion machine is a hypothetical machine that can work infinitely without an external energy source.

Answer: B
Explanation:
Cloud seeding is a weather modification technique that improves a cloud’s ability to produce rain or snow by introducing tiny ice nuclei into certain types of subfreezing clouds. These nuclei provide a base for raindrops or snowflakes to form.

Answer: D
Explanation:
An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. Apart from military purposes, drones are used in aerial photography, precision agriculture, forest fire monitoring policing and surveillance, infrastructure inspections, product deliveries and so on.
The DRDO has developed many drones for Indian defence forces and many more are in various stages of development.
• Pair 1 is incorrectly matched: Lakshya is a high-speed target drone system for discreet aerial reconnaissance of battlefield and target acquisition.
• Pair 2 is incorrectly matched: Rustom is medium altitude long endurance drone system having an altitude ceiling is 25000 feet. It has an endurance of 12-15 hours and can carry pay load of 75 kilograms.
• Pair 3 is incorrectly matched: The Nishant UAV is primarily tasked with intelligence gathering and surveillance over enemy territory. It is Tapas BH drone which has been developed for Beyond Horizon applications.

Answer: C
Explanation:
• The purpose of stealth technology is to make military machines remain invisible as much as possible. They are designed to avoid getting detected through radio signals, light, ultrasonic waves and so on.
• Fighter aircraft, drones, satellites, submarines, missiles and even ground vehicles are made with stealth technology to make operations covert and impactful.
• For example- the aircraft can be shaped so that it reflects radar signals away from the radar equipment or it can be covered in materials that absorb radar signals.
• Radar, Sonar, and other methods are used to detect the presence of enemy machines.
• Small satellites which are smaller than the size of a pen go undetected even if observed through the best of telescopes. So, radars are used to detect small satellites. Stealth technology in satellites try to negate this detection.

Answer: C
Explanation:
• An aircraft carrier is roughly 700-1000 feet which is more than 10 times shorter than a typical runway required for small planes like Airbus A320. A fighter plane needs to gather takeoff speed in a very short length. It is not possible to just roll on the deck of the aircraft carrier to achieve the takeoff speed. So, catapult assisted takeoff is used to give initial thrust to planes just like a catapult using hydraulic and air compressors. CATOBAR is the technology used for this.
CATOBAR
CATOBAR stands for Catapult Assisted Take-off but Arrested Recovery. We know the working mechanism of Catapult. The energy is stored in it. When this energy is released, it gets covered in kinetic energy. Due to this, the object placed on the catapult is launched with the speed. The same mechanism is applied to aircraft carriers.

Answer: A
Context: The International Thermonuclear Experimental Reactor (ITER) is already billions of dollars over budget and decades behind schedule. Not even its leaders can say how much more money and time it will take to complete. It run the risk of turning into one of the largest scientific disasters in the history of mankind. ITER is supposed to help humanity achieve the dream of a world powered not by fossil fuels but by fusion energy, the same process that makes the stars shine.
Explanation:
• Statement 1 is correct: Fusion reactions is intrinsically safe and is not expected to produce high activity or long-lived nuclear waste. Furthermore, as the fusion process is difficult to start and maintain, there is no risk of a runaway reaction and meltdown.
• Statement 2 is correct and is correct explanation of Statement 1: Fusion can only occur under strict operational conditions, outside of which (in the case of an accident or system failure, for example), the plasma will naturally terminate, lose its energy very quickly and extinguish before any sustained damage is done to the reactor. Importantly, nuclear fusion — just like fission — does not emit carbon dioxide or other greenhouse gases into the atmosphere, so it could be a long-term source of low-carbon electricity in future.

Answer: A
Explanation:
Cholesterol is a type of lipid (fat) that helps our body perform many important functions. Cholesterol is a waxy substance. It is not necessarily bad as our body needs it to build cells and make vitamins and other hormones. Cholesterol circulates in the blood. As the amount of cholesterol in our blood increases, so does the risk to our health. High cholesterol contributes to a higher risk of cardiovascular diseases, such as heart disease and stroke.
• Statement 1 is incorrect: Cholesterol is made up of fat and protein known as Lipoprotein. Lipoproteins are round particles made of fat (lipids) and proteins that travel in our bloodstream and reaches cells of our body. Cholesterol and triglycerides are two types of lipids found in lipoproteins.
• Statement 2 is correct: About 80% of our daily requirements are produced by the liver in the human body. However, it is also found in fatty foods like egg, meat and vegetable oil.
• Statement 3 is incorrect: HDL cholesterol is known as good cholesterol whereas LDL cholesterol is known as bad cholesterol. This is because HDL cholesterol does not get deposited in the arteries whereas LDL cholesterol may stick to the artery wall. Too much cholesterol in the arteries may lead to a buildup of plaque known as atherosclerosis. This can increase the risk of blood clots in the arteries. Ultimately it can trigger cardiac arrest or heart stroke.

Answer: A
Explanation:
Machine Learning and Deep Learning are the two main concepts of Data Science and the subsets of Artificial Intelligence.
Machine Learning allows the computers to learn from the experiences by its own, use statistical methods to improve the performance and predict the output without being explicitly programmed.
Deep Learning is inspired by the functionality of human brain cells, which are called neurons, and leads to the concept of artificial neural networks. It is also called a deep neural network or deep neural learning.
• Statement 1 is correct: Machine Learning algorithm is data driven. It follows a structured format for solving problems and thus is mainly employed for simpler tasks like predicting customer choice on e-commerce site. But Deep Learning mimics complex neural schemas of human brain. It is adept at solving complex problems which require parallel processing.
• Statement 2 is incorrect: Deep Learning is a subset of Machine Learning. Deep Learning is a special case of machine learning in which each step is checked in a more elaborated manner.

Answer: B
Context: There is a possibility of using photonic laser thrust, a technology that does exist, as a new system to propel spacecraft to relativistic speeds, allowing them to travel farther than ever before. Conventional fuel-based rockets will likely take us to Mars and probably enable us to reach even more distant destinations in the solar system. However, we will not realistically be able to travel outside the Solar System with the use of rocket fuel. We need something which can propel us to relativistic speed (comparable to the speed of light).
Explanation:
• Statement 1 is incorrect: According to the special theory of relativity, photons are massless particles. But they travel at the speed of light which proves that they possess momentum and kinetic energy. This momentum will be used to generate thrust to propel spacecraft at a very high speed.
• Statement 2 is correct: Just like sail is used in boats wherein, wind hits the canvas which pushes the boat forward. In the same manner solar sail is a method of spacecraft propulsion using radiation pressure exerted by sunlight on large surfaces. High-energy laser beams can also be used as an alternative light source to exert much greater force than would be possible using sunlight, a concept known as beam sailing. This is the main working principle of photonic propulsion.