Daily Quiz: UPSC Prelims Marathon (Science & Technology) – June 11, 2020

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 as a circular arc in the sky. It is often visible after rainfall due to highly humid atmosphere and absence of air pollution. The position of the sun and the raindrops in relation to the observer need to be just right for a rainbow to form:

• The sun needs to be behind the viewer
• The sun needs to be low in the sky, at an angle of less than 42° above the horizon. The lower the sun in the sky the more of an arc of a rainbow the viewer will see
• Rain, fog or some other source of water droplets must be in front of the viewer

The size of the raindrops does not directly affect the geometry of a rainbow, but mist or fog tends to disperse the effect more. Rainbows only appear semi-circular over level ground at sunrise or sunset, when the sun is exactly on the horizon, the majority of the time a smaller segment of an arc is seen.

Optical fibre is a device which works on the principle of total internal reflection by which light signals can be transmitted from one place to another with negligible loss of energy.

Double rainbow.

Statement 1 is correct: Double rainbows are formed when sunlight is reflected twice within a raindrop with the violet light that reaches the observers eye coming from the higher raindrops and the red light from lower raindrops.

Statement 2 is correct: A key feature of double rainbows is that the colour sequence in the second rainbow is reversed, ROYGBIV instead of VIBGYOR order in primary rainbow.

Cadmium is a heavy metal with a high toxicity. Cadmium is toxic at very low exposure levels and has acute and chronic effects on health and environment. Cadmium is not degradable in nature and will thus, once released to the environment, stay in circulation.

• The major natural sources for mobilizations of cadmium from the earth’s crust are volcanoes and weathering of rocks.
• Within the biosphere the cadmium is trans-located by different processes. The major sources for emission to air from natural sources are volcanoes, airborne soil particles, sea spray, biogenic material and forest fires.

Gas hydrates.

• Gas hydrates are formed when a gas such as methane gets trapped in well-defined cages of water moleculesforming crystalline solids.
• In terrestrial conditions, gas hydrates are formed naturally under the sea bed and glaciers under high pressure, low temperature conditions. Methane hydrate is a potential source of natural gas.
• Researchers at Indian Institute of Technology (IIT) Madrashave experimentally shown that methane and carbon dioxide (CO2) can exist as gas hydrates at temperatures and pressures seen in interstellar atmosphere.

The methane and CO2 hydrates were produced in the lab at very low pressures (ten thousand billionth of atmospheric pressure) and temperature (as low as -263 degree C) to simulate the conditions of deep space.

Botulinum is a natural toxin produced by a bacterium known as Clostridium botulin. It produces the toxin when it starts reproducing.

• The bacterium is commonly found in the soil, river, and sea water.
• There are around eight types— A, B, C1, C2, D, E, F, and G — of botulinum toxin and they are distinguishable when diagnosed. But all types of toxins attack the neurons, which leads to muscle paralysis.
• Botulinum affects both humans and animalsbut the type of the toxin varies — botulinum C in birds and A, B and E in humans.  The toxin has been recognised as a major cause of mortality in wild birds since the 1900s.

Avian botulism killed over 18,000 birds in and around Rajasthan’s Sambhar Lake.

Gluten.

• Gluten is a family of storage proteins — formally known as prolamins — that are naturally found in certain cereal grains, such as wheat, barley, and rye.
• Gluten offers a variety of functional culinary benefits and is responsible for the soft, chewy texture that is characteristic of many gluten-containing, grain-based foods.
• Because of these unique physical properties, gluten is also frequently used as an additive to improve texture and promote moisture retention in a variety of processed foods.

Gluten may be found in a variety of whole and processed foods, including:

• Grains:whole wheat, wheat bran, barley, rye, triticale, spelt, kamut, couscous, farro, semolina, bulgur, farina, einkorn, durum, wheat germ, cracked wheat, matzo, mir (a cross between wheat and rye)
• Processed grain-based products: crackers, bread, breadcrumbs, pasta, seitan, wheat-containing soba noodles, some veggie burgers, cookies, pastries
• Other foods and beverages: barley malt, malt vinegar, soy sauce, certain salad dressings, sauces or gravies thickened with flour, bouillon and some broths, certain spice blends, flavored chips, beer, certain kinds of wine

The monkeys are divided into two main groups—Old World and New World monkeys. The term “old world” refers to the areas (Europe, Africa, and Asia) known to the Europeans prior to the discovery of the “new world” (the Americas).

• New World monkeys are members of five different primate families (Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae) and consist of almost exclusively arboreal (tree-dwelling) species like marmosets, tamarins, capuchins, and spider monkeys.
• Old World monkeys belong to the family Cercopithecidae and consist of species such as macaques, baboons, and vervet monkeys.
• These monkeys spend much more of their time on the ground, but can be found in habitats ranging from the rainforest to the savannah to the mountains.

Ever since researchers sequenced the chimp genome in 2005, they have known that humans share about 99% of our DNA with chimpanzees, making them our closest living relatives.

• But there are actually two species of apes that are this closely related to humans: bonobos (Pan paniscus) and the common chimpanzee (Pan troglodytes).

This has prompted researchers to speculate whether the ancestor of humans, chimpanzees, and bonobos looked and acted more like a bonobo, a chimpanzee, or something else—and how all three species have evolved differently since the ancestor of humans split with the common ancestor of bonobos and chimps between 4 million and 7 million years ago in Africa.

Measles.

• Measles is caused by a virus in the paramyxovirusfamily and it is normally passed through direct contact and through the air.
• The virus infects the respiratory tract, and then spreads throughout the body. Measles is a human disease and is not known to occur in animals.
• Measles is a highly contagious, serious disease caused by a virus. Before the introduction of measles vaccine in 1963 and widespread vaccination, major epidemics occurred approximately every 2–3 years and measles caused an estimated 2.6 million deaths each year.
• Accelerated immunization activities have had a major impact on reducing measles deaths. During 2000– 2018, measles vaccination prevented an estimated 23.2 million deaths. Global measles deaths have decreased by 73% from an estimated 536000 in 2000 to 142,000 in 2018.