Insights Static Quiz -29, 2018

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.