General Science Test 1

Solution: d)

It is a modified previous year UPSC question.

First statement is right as it is its particle nature of light that scatters it. (https://sciencing.com/diffused-light-5470956.html)

Second statement is correct. Light is diffused after being scattered by particles in atmosphere (or in any medium)

Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself. This involves gas molecules.

Solution: d)

It is a modified previous year UPSC question.

Most of us will have used a product containing sodium sulfate, though oddly it is present in a role that has no practical function. Powdered detergents for washing clothes usually contain sodium sulfate simply to bulk up the product, making detergent manufacturers the biggest users of the compound. It does nothing for the wash, but as a very cheap, pH neutral substance that readily dissolves in warm water, it simply passes through the system, making the product less costly to produce per unit weight. There isn’t as much of it around as there used to be, though, as powder has declined in popularity and there is no need for filler in liquids and gels. Our compound is sometimes confused with sodium lauryl sulfate (also known as sodium dodecyl sulfate) and sodium laureth sulfate which are surfactants used in a range of cleaning products from detergents to toothpastes, but both these compounds are quite complex organic structures which aren’t produced from basic sodium sulfate.

Our sulfate also turns up as a fining agent – not in the more familiar environment of wine or beer fining, but in making glass. In the alcoholic drinks, the fining agent’s role is to extract organic substances that make the liquid cloudy, where in glass it picks up scum and prevents small bubbles from forming. But perhaps the most interesting application of sodium sulfate is in the rapidly advancing world of solar energy heat storage.

As solar thermal power plants, which concentrate incoming light with mirrors to store energy in the form of heat, become more common, there is a need to hold onto that heat before using it. Sodium sulfate takes a high amount of energy to change from solid to liquid and goes through a second phase change at around 32 degrees Celsius when it changes to the anhydrous form, which means that it can store considerably more heat energy than would be expected for any particular mass. Although it isn’t appropriate for the high temperature systems that store heat directly from solar collectors, it has the potential to be valuable in secondary solar facilities, for instance where the heated material gradually releases the heat to warm a building.

Second statement is wrong as it’s Sodium silicate that is used to keep washing powder dry. (https://www.marketizer.com/articles/uses-and-applications-of-liquid-and-solid-sodium-silicate-2735414.htm)

Solution: d)

A transverse wave is a moving wave that consists of oscillations occurring perpendicular (right angled) to the direction of energy transfer (or the propagation of the wave).

If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y–z plane.

Light is an example of a transverse wave, while sound is a longitudinal wave. A ripple in a pond and a wave on a string are easily visualized as transverse waves.

Longitudinal waves are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of propagation of the wave. Mechanical longitudinal waves are also called compressional or compression waves, because they produce compression and rarefaction when traveling through a medium, and pressure waves, because they produce increases and decreases in pressure.

Solution: b)

It is also based on previous UPSC question.

Option A is wrong as it is oxides of nitrogen

Option B is wrong, as photochemical smog requires sunlight and occurs in the morning or in afternoon

Option C is right ( see explanation below – second paragraph)

Photochemical smog forms from a complex process, however the source of it is quite apparent. The largest contributor is automobiles, while coal-fired power plants and some other power plants also produce the necessary pollutants to facilitate its production. Due to its abundance in areas of warmer temperatures, photochemical smog is most common in the summer.^[3]

It forms in the morning when a tremendous number people are driving their vehicles to work. Nitrogen oxides produced in the car engine are introduced into the atmosphere, which may combine with water to form nitric acid or react with sunlight to produce singular oxygen atoms, which then combine with molecular oxygen to produce ozone.^[2] The nitric acid may precipitate to the Earth resulting in acid rain, or remain in the smog. Due to the direct production of it by vehicles, the smog forms over cities where many people may encounter its adverse health effects.

Hotter days mean more photochemical smog, especially in the densely populated cities such as those mentioned above. As more and more urban populations arise around the globe, this problem is only expected to increase.

http://energyeducation.ca/encyclopedia/Photochemical_smog

Solution: d)

Based on previous year UPSC question on sound waves

Air is a gas, and a very important property of any gas is the speed of sound through the gas. Why are we interested in the speed of sound? The speed of “sound” is actually the speed of transmission of a small disturbance through a medium. Sound itself is a sensation created in the human brain in response to sensory inputs from the inner ear. (We won’t comment on the old “tree falling in a forest” discussion!)

Disturbances are transmitted through a gas as a result of collisions between the randomly moving molecules in the gas. The transmission of a small disturbance through a gas is an isentropic process. The conditions in the gas are the same before and after the disturbance passes through. Because the speed of transmission depends on molecular collisions, the speed of sound depends on the state of the gas. The speed of sound is a constant within a given gas and the value of the constant depends on the type of gas (air, pure oxygen, carbon dioxide, etc.) and the temperature of the gas.

The speed of sound in the atmosphere is a constant that depends on the altitude, but an aircraft can move through the air at any desired speed. The ratio of the aircraft’s speed to the speed of sound affects the forces on the aircraft. Aeronautical engineers call the ratio of the aircraft’s speed to the speed of sound the Mach number, M. If the aircraft moves much slower than the speed of sound, conditions are said to be subsonic, 0 < M << 1, and compressibility effects are small and can be neglected. If the aircraft moves near the speed of sound, conditions are said to be transonic, M ~ 1, and compressibility effects like flow choking become very important. For aircraft speeds greater than the speed of sound, conditions are said to be supersonic, 1 < M < 3, and compressibility effects are important. Depending on the specific shape and speed of the aircraft, shock wavesmay be produced in the supersonic flow of a gas. For high supersonic speeds, 3 < M < 5, aerodynamic heating becomes very important. If the aircraft moves more than five times the speed of sound, conditions are said to behypersonic, M > 5, and the high energy involved under these conditions has significant effects on the air itself. The Space Shuttle re-enters the atmosphere at high hypersonic speeds, M ~ 25. Under these conditions, the heated air becomes an ionized plasma of gas and the spacecraft must be insulated from the high temperatures.

https://www.grc.nasa.gov/www/k-12/airplane/sound.html

Solution: d) 

Clouds are composed primarily of small water droplets and, if it’s cold enough, ice crystals. The vast majority of clouds you see contain droplets and/or crystals that are too small to have any appreciable fall velocity. So the particles continue to float with the surrounding air. For an analogy closer to the ground, think of tiny dust particles that, when viewed against a shaft of sunlight, appear to float in the air.

Indeed, the distance from the center of a typical water droplet to its edge–its radius–ranges from a few microns (thousandths of a millimeter) to a few tens of microns (ice crystals are often a bit larger). And the speed with which any object falls is related to its mass and surface area–which is why a feather falls more slowly than a pebble of the same weight. For particles that are roughly spherical, mass is proportional to the radius cubed (r³); the downward-facing surface area of such a particle is proportional to the radius squared (r²). Thus, as a tiny water droplet grows, its mass becomes more important than its shape and the droplet falls faster. Even a large droplet having a radius of 100 microns has a fall velocity of only about 27 centimeters per second (cm/s). And because ice crystals have more irregular shapes, their fall velocities are relatively smaller. 

Upward vertical motions, or updrafts, in the atmosphere also contribute to the floating appearance of clouds by offsetting the small fall velocities of their constituent particles. Clouds generally form, survive and grow in air that is moving upward. Rising air expands as the pressure on it decreases, and that expansion into thinner, high-altitude air causes cooling. Enough cooling eventually makes water vapor condense, which contributes to the survival and growth of the clouds. Stratiform clouds (those producing steady rain) typically form in an environment with widespread but weak upward motion (say, a few cm/s); convective clouds (those causing showers and thunderstorms) are associated with updrafts that exceed a few meters per second. In both cases, though, the atmospheric ascent is sufficient to negate the small fall velocities of cloud particles.

Another way to illustrate the relative lightness of clouds is to compare the total mass of a cloud to the mass of the air in which it resides. Consider a hypothetical but typical small cloud at an altitude of 10,000 feet, comprising one cubic kilometer and having a liquid water content of 1.0 gram per cubic meter. The total mass of the cloud particles is about 1 million kilograms, which is roughly equivalent to the weight of 500 automobiles. But the total mass of the air in that same cubic kilometer is about 1 billion kilograms–1,000 times heavier than the liquid!

So, even though typical clouds do contain a lot of water, this water is spread out for miles in the form of tiny water droplets or crystals, which are so small that the effect of gravity on them is negligible. Thus, from our vantage on the ground, clouds seem to float in the sky.

https://www.scientificamerican.com/article/why-do-clouds-float-when/

Solution: b)

Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called enzymology and a new field of pseudoenzyme analysis has recently grown up, recognising that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual ‘pseudocatalytic’ properties.

Enzymes are known to catalyze more than 5,000 biochemical reaction types.[4] Most enzymes are proteins, although a few are catalytic RNA molecules. The latter are called ribozymes. Enzymes’ specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the reaction rate by lowering its activation energy. Some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5′-phosphate decarboxylase, which allows a reaction that would otherwise take millions of years to occur in milliseconds.

Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, nor do they alter the equilibrium of a reaction. Enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules: inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity. Many therapeutic drugs and poisons are enzyme inhibitors.

An enzyme’s activity decreases markedly outside its optimal temperature and pH. Some enzymes are used commercially, for example, in the synthesis of antibiotics. Some household products use enzymes to speed up chemical reactions: enzymes in biological washing powders break down protein, starch or fat stains on clothes, and enzymes in meat tenderizer break down proteins into smaller molecules, making the meat easier to chew.

There are some enzymes which are made up of RNA (ribozymes)

Solution: d)

Antibiotics also called antibacterials, are a type of antimicrobial[1] drug used in the treatment and prevention of bacterial infections.  They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics. Sometimes the term antibiotic (which means “opposing life”) is used to refer to any substance used against microbes,[6] synonymous with antimicrobial.

Some sources distinguish between antibacterial and antibiotic; antibacterials are used in soaps and disinfectants, while antibiotics are used as medicine.[8] Antibiotics revolutionized medicine in the 20th century.[9] However, their effectiveness and easy access have also led to their overuse, prompting bacteria to develop resistance.

This has led to widespread problems, so much as to prompt the World Health Organization to classify antimicrobial resistance as a “serious threat [that] is no longer a prediction for the future, it is happening right now in every region of the world and has the potential to affect anyone, of any age, in any country”

http://www.who.int/mediacentre/factsheets/fs194/en/

Solution: c)

There are five groups of marine mammals:  pinnipeds (seals, sea lions, fur seals, and walruses), cetaceans (whales, dolphins, and porpoises), sea otters, sirenians (dugongs and manatees), and polar bears.

Steller’s sea cow (Hydrodamalis gigas) is an extinct sirenian discovered by Europeans in 1741. At that time, it was found only around the Commander Islands in the Bering Sea between Alaska and Russia; its range was more extensive during the Pleistocene epoch, and it is possible that the animal and humans previously interacted.

As question asks only “living mammals’ – sea cow is wrong as it’s extinct.

http://www.bbc.com/earth/story/20150613-the-giant-cow-that-swam-the-ocean

Solution: d)

Similar question was asked by UPSC in 2012

Fogbows, similar to rainbows form in the same way as rainbows, but they are formed by much smaller cloud and fog droplets that diffract light extensively.

Supernumerary rainbows cannot be explained using classical geometric optics. The alternating faint bands are caused by interference between rays of light following slightly different paths with slightly varying lengths within the raindrops. Some rays are in phase, reinforcing each other through constructive interference, creating a bright band; others are out of phase by up to half a wavelength, cancelling each other out through destructive interference, and creating a gap. Given the different angles of refraction for rays of different colours, the patterns of interference are slightly different for rays of different colours, so each bright band is differentiated in colour, creating a miniature rainbow. Supernumerary rainbows are clearest when raindrops are small and of uniform size.

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky.

https://en.wikipedia.org/wiki/Rainbow#Explanation

You may debate Interference and diffraction, but as rainbows include variety of types, it’s safe to assume even interference and diffraction play certain role in formation of rainbows.

Solution: a)

The primary function of the small intestine is the absorption of nutrients and minerals from food, using small finger-like protrusions called villi. (Hence statement 1 is wrong)

In the small intestine, structurally, the mucosa is covered in wrinkles or folds called plicae circulares, which are considered permanent features in the wall of the organ. They are distinct from rugae which are considered non-permanent or temporary allowing for distention and contraction. From the plicae circulares project microscopic finger-like pieces of tissue called villi (Latin for “shaggy hair”). The individual epithelial cells also have finger-like projections known as microvilli. The functions of the plicae circulares, the villi, and the microvilli are to increase the amount of surface area available for the absorption of nutrients, and to limit the loss of said nutrients to intestinal fauna.

Solution: d)

First 3 are the functions of spleen (check here: https://en.wikipedia.org/wiki/Spleen#Function)

Last one is the function of liver.

Previously UPSC has asked question on functions of pancreas.

Solution: b)

Novichok is a series of nerve agents the Soviet Union and Russia developed between 1971 and 1993. Russian scientists who developed the agents claim they are the deadliest nerve agents ever made, with some variants possibly five to eight times more potent than VX, and others up to ten times more potent than soman.

Novichok agents have never been used on the battlefield. Theresa May, Prime Minister of the United Kingdom, said that one such agent was used in the poisoning of Sergei and Yulia Skripal in England in March 2018.[10] Russia officially denies producing or researching Novichok agents.

A pulmonary agent, or choking agent, is a chemical weapon agent designed to impede a victim’s ability to breathe. They operate by causing a build-up of fluids in the lungs, which then leads to suffocation. Exposure to the eyes and skin tends to be corrosive, causing blurred vision and severe deep burns. Inhalation of these agents cause burning of the throat, coughing, vomiting, headache, pain in chest, tightness in chest, and respiratory and circulatory failure. Example – chlorine gas.

Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer messages to organs. The disruption is caused by the blocking of acetylcholinesterase, an enzyme that catalyzes the breakdown of acetylcholine, a neurotransmitter.

Solution: d)

Polar bear is considered as ocean mammal. (http://www.marinemammalcenter.org/education/marine-mammal-information/)

Check here photos of freshwater mammals:

https://www.nationalgeographic.com/environment/photos/freshwater-mammals/

Solution: c)

Serum albumin is the most abundant blood plasma protein and is produced in the liver and forms a large proportion of all plasma protein. The human version is human serum albumin, and it normally constitutes about 50% of human plasma protein. Serum albumins are important in regulating blood volume by maintaining the oncotic pressure (also known as colloid osmotic pressure) of the blood compartment.

They also serve as carriers for molecules of low water solubility this way isolating their hydrophobic nature, including lipid-soluble hormones, bile salts, unconjugated bilirubin, free fatty acids (apoprotein), calcium, ions (transferrin), and some drugs like warfarin, phenobutazone, clofibrate & phenytoin. For this reason, it is sometimes referred as a molecular “taxi”. Competition between drugs for albumin binding sites may cause drug interaction by increasing the free fraction of one of the drugs, thereby affecting potency.

Solution: c)

Vulcanization or vulcanisation is a chemical process for converting natural rubber or related polymers into more durable materials by heating them with sulfur[1] or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains.

Advantages of Vulcanized rubber:

• It has good tensile strength and extensibility.
• Excellent resilience i.e.it returns to the original shape, when the deforming load is removed.
• Low water absorption tendency.
• Higher resistance to oxidation, wear and tear abrasion.
• Better electrical insulator.
• It is resistant to organic solvents (petro, benzene), fats and oils.
• It has higher useful temperature range unlike uncured rubber which becomes soft at high temperature(>335K) and brittle at low temperatures (<283K)

Solution: b)

A breeder reactor is a nuclear reactor that generates more fissile material than it consumes.[1] These devices achieve this because their neutron economy is high enough to breed more fissile fuel than they use from fertile material, such as uranium-238 or thorium-232. Breeders were at first found attractive because their fuel economy was better than light water reactors, but interest declined after the 1960s as more uranium reserves were found,[2] and new methods of uranium enrichment reduced fuel costs.

Solution: b)

Though all statements are correct, Option – B explains better why optic fiber is better than copper.

So what gives it the technical edge over copper wires?

Traditional copper wires transmit electrical currents, while fibre optic technology sends pulses of light generated by a light emitting diode or laser along optical fibres.

“In both cases you’re detecting changes in energy, and that’s how you encode data.

“With copper wires you’re looking at changes in the electromagnetic field, the intensity of that field and perhaps the phase of the wave being sent down a wire.

“With fibre optics, a transmitter converts electronic information into pulses of light — a pulse equates to a one, while no pulse is zero. When the signal reaches the other end, an optical receiver converts the light signal back into electronic information,” explains Malaney.

The throughput of the data is determined by the frequency range that a cable will carry — the higher the frequency range, the greater the bandwidth and the more data that can be put through per unit time.

And this is the key difference — fibre optic cables have much higher bandwidths than copper cables.

“Optical fibre can carry much higher frequency ranges — note that light is a very high frequency signal — while copper wire attenuates or loses signal strength at higher frequencies,” says Malaney.

Also, fibre optic technology is far less susceptible to noise and electromagnetic interference than electricity along a copper wire.

“You can send the signal for over 200 kilometres without any real loss of quality while a copper cable signal suffers a lot of degradation over that distance,” says Malaney.

Solution: c)

Natural uranium can be used to fuel both low- and high-power nuclear reactors. Historically, graphite-moderated reactors and heavy water-moderated reactors have been fueled with natural uranium in the pure metal (U) or uranium dioxide (UO2) ceramic forms. However, experimental fuelings with uranium trioxide (UO3) and triuranium octaoxide, (U3O8) have shown promise.[2] The 0.72% uranium-235 is not sufficient to produce a self-sustaining critical chain reaction in light water reactors or nuclear weapons; these applications must use enriched uranium.

Nuclear weapons take a concentration of 90% uranium-235, and light water reactors require a concentration of roughly 3% uranium-235.[3] Unenriched natural uranium is appropriate fuel for a heavy-water reactor, like a CANDU reactor.

https://en.wikipedia.org/wiki/Natural_uranium

Solution: b)

The bulk (96%) of the byproduct from enrichment is depleted uranium (DU), which can be used for armor, kinetic energy penetrators, radiation shielding and ballast. As of 2008 there are vast quantities of depleted uranium in storage. The United States Department of Energy alone has 470,000 tonnes.[1] About 95% of depleted uranium is stored as uranium hexafluoride (UF6).

(nuclear related questions are favourite with UPSC, hence these questins)