General Science Mixed Quiz: Set 172

Light travels fastest in vacuum and almost as fast in air, so in any material medium it moves more slowly than in air, and the ratio of the two speeds is greater than one.

Speleology is the exploration and scientific study of caves, their formation, the limestone features such as stalactites and stalagmites that develop in them, and the animal life adapted to permanent darkness.

A magnetic field pushes a moving charge sideways, and the push on a negative charge is opposite to that on a positive one, so the two kinds bend away from each other.

In the electrolytic refining of copper, a solution of copper sulphate made acidic with a little dilute sulphuric acid carries the copper ions between the electrodes.

Isobars are atoms of different elements with the same mass number, and 18 + 22 gives a mass number of 40, the same as calcium.

When light of a suitable frequency falls on a metal and knocks electrons out of it, the process is called photoelectric emission.

Breaking lead nitrate into lead oxide, nitrogen dioxide and oxygen needs a steady supply of heat, so the reaction absorbs energy and is endothermic.

Clay is a plastic material: it deforms permanently under even a small force, so its stress is not proportional to its strain.

A honeybee sting injects methanoic acid, also called formic acid (HCOOH), which causes the burning pain and irritation.

A perfectly horizontal rope has no upward component of tension, so no finite tension can hold up the 200 N weight with the rope fully straight.

Germanium is a metalloid, an element whose properties lie between those of metals and non-metals. It is a hard, shiny, grey-white solid like a metal, yet it is brittle and conducts electricity far less well than a metal, which makes it a semiconductor.

Muga silk comes from Antheraea assamensis, reared on Som and Soalu trees of the Brahmaputra valley, and Assam's muga carries a Geographical Indication tag.

Sulphur vapour turns straight into solid sulphur on the cooler rocks without first becoming a liquid, and a direct change from gas to solid is called deposition.

The restoring force on the bob is mg sin θ. For small angles sin θ is almost equal to θ, so the force becomes proportional to the displacement and points back towards the mean position.

Sulphur dissolves completely in carbon disulphide, so the two form a true solution, and a solution is a homogeneous mixture.

A beam seen from the side is visible only because tiny particles send some of its light sideways. Light travelling in a straight line cannot enter our eyes unless something redirects it towards us.

An object floats when its average density is less than that of the liquid and sinks when it is greater.

The gap between an object and its real image is smallest when the object is placed at 2F, twice the focal length from the lens.

A p-type semiconductor is made by adding a small amount of a trivalent impurity, such as boron, aluminium, gallium or indium, to pure silicon or germanium.

Bronze is made by mixing copper (Cu) with tin (Sn), usually about nine parts copper to one part tin. Adding tin makes the metal harder, stronger and more resistant to corrosion than pure copper, which is why bronze was used for tools, weapons, bells, coins and statues.