General Science Questions and Answers

Answer: A

Rayon is chemically cellulose. It is made by dissolving wood pulp and forcing the solution through fine holes into an acid bath, where the cellulose is regenerated as a filament.

Because it comes from a natural polymer rather than being built from small molecules, rayon is called a regenerated fibre rather than a true synthetic.

Answer: D

Optical fibres are used mainly for communication. A signal is sent as pulses of light along a glass fibre, kept inside it by total internal reflection.

A single fibre carries far more information than a copper cable, over much greater distances, and is immune to electrical interference. Submarine fibre cables carry almost all intercontinental internet traffic.

Answer: C

Amla, the Indian gooseberry, is among the richest natural sources of vitamin C - about 600 mg per 100 g, some twenty times that of an orange.

Its vitamin C is also unusually stable to heat and drying, because tannins in the fruit protect it from oxidation.

Answer: A

Bauxite is the chief ore of aluminium, a mixture of hydrated aluminium oxides.

The oxide is extracted from it by the Bayer process and then reduced to the metal by electrolysis in molten cryolite. Calamine is a zinc ore, calcite calcium carbonate, and galena lead sulphide.

Answer: A

A rainbow's colours come from the dispersion of sunlight in raindrops.

Each drop refracts the light on entry, reflects it once off the back and refracts it again on leaving. Because the refractive index varies slightly with wavelength, the colours emerge at different angles - red at about 42°, violet at 40°.

Answer: D

Tulsi, holy basil, is called the herbal Indian doctor.

It is the most widely used plant in Ayurveda, taken for coughs, fever and digestive complaints, and is grown in the courtyard of many Indian homes.

Answer: C

Ethanol as a biofuel is obtained chiefly from sugarcane.

Molasses, the residue after sugar is crystallised, is fermented by yeast into ethanol and distilled. Brazil and India both blend it with petrol; sugarcane is more efficient than grain because its sugar needs no conversion from starch first.

Answer: C

The stimulant in tea is caffeine - about 20 to 60 mg in a cup, roughly half that of coffee.

Tannins give tea its astringency and colour but are not stimulants. The caffeine in tea is sometimes called theine, but it is the same compound.

Answer: B

Ornithology is the study of birds, from the Greek ornis.

Salim Ali, the Birdman of India, was the country's best-known ornithologist and the author of the standard handbook of Indian birds.

Answer: B

Rice is not a rabi crop - it is the main kharif crop, sown with the monsoon in June and July.

Wheat, mustard and gram are rabi crops, sown in October and November and harvested in March and April on residual moisture and irrigation.