General Science GK Questions with Answers – Page 126

Roasting means heating a sulphide ore strongly in plenty of air, so that the sulphide turns into an oxide and the sulphur escapes as sulphur dioxide gas.

Kwashiorkor is caused by a severe lack of protein in the diet, even when the child gets some calories from starchy food.

Mature red blood cells, or erythrocytes, lose their nucleus before they enter the blood. Losing the nucleus, and the mitochondria too, leaves more room for haemoglobin, the iron-rich protein that carries oxygen, and gives the cell its flexible biconcave disc shape, which lets it squeeze through narrow capillaries.

It is the main growth inhibitor among plant hormones and works against the growth promoters.

For a lens, magnification m is the image height divided by the object height, which also equals v divided by u. A plus sign means the image is erect and virtual, and a value of 2 means it is twice as tall as the object.

Starlight has to cross many layers of air before it reaches the eye, and these layers keep changing in temperature and density, so their refractive index keeps changing too.

Isaac Newton built the first practical reflecting telescope in 1668. In it, light from the star falls on a large concave mirror at the bottom of the tube, and a small flat mirror set at 45 degrees near the top turns the light sideways to the eyepiece.

Levers are grouped by where the fulcrum, the load and the effort sit. In a second class lever the load lies between the fulcrum and the effort.

Each human kidney has about one million nephrons, and every nephron begins with a cup-shaped Bowman's capsule that encloses a knot of capillaries called the glomerulus.

Vitamin D helps the intestine absorb calcium and phosphorus, so without it the bones of a growing child stay soft and bend, giving bow legs, a pigeon chest and a large forehead; this disease is rickets.

LIGO, the Laser Interferometer Gravitational-Wave Observatory in the USA, detected gravitational waves for the first time in September 2015 (announced in February 2016), and such waves were predicted by Einstein's general theory of relativity in 1916.

Milk of magnesia is a white suspension of magnesium hydroxide, Mg(OH)2, in water, and its milky look gives it the name.

Galvanisation is the coating of iron or steel with a thin layer of zinc so that the iron underneath does not rust.

A lactometer floats in milk and shows its relative density. Pure milk is denser than water, so adding water lowers the density and the instrument sinks deeper, which reveals the adulteration.

The horsepower is an older practical unit of power that survives in the rating of engines, pumps and motors, and it equals about 746 watts.

The mole is the chemist's counting unit: one mole of any substance contains the Avogadro number of particles, about six followed by twenty-three zeros, whether those particles are atoms, molecules or ions.

A barometer measures the pressure of the atmosphere, traditionally by balancing it against a column of mercury. It is also used for forecasting weather, because a sudden drop in pressure signals an approaching storm, and for finding altitude, since pressure falls as one rises.

Work is force multiplied by displacement. Force has the dimensions M L T⁻², and multiplying it by a length adds one more power of L, which gives M L² T⁻².

Pressure is force divided by area, so its unit is one newton per square metre, which is given the name pascal after Blaise Pascal.

A light year is the distance that light, moving at about three lakh kilometres per second, covers in one year, which works out to roughly 9.46 trillion kilometres.