General Science GK Questions with Answers – Page 8

Sound is a mechanical wave, so it needs a medium, and in air its particles vibrate along the direction of travel.

Tiny gas molecules in the air scatter short wavelengths far more strongly than long ones. This is Rayleigh scattering: the amount of scattering varies inversely with the fourth power of the wavelength.

During a sprint the muscles need energy faster than the blood can supply oxygen, so they switch to anaerobic respiration and lactic acid builds up.

Fluorine cannot be detected by Lassaigne's test, because silver fluoride is soluble in water and gives no precipitate. Lassaigne's test, or the sodium fusion test, detects nitrogen, sulphur and halogens in an organic compound.

Analogous structures do the same job but evolved separately, and the wings of birds and bats are a standard example.

Planaria is a free-living flatworm, while the other three are parasites that live inside a host. Planaria belongs to the phylum Platyhelminthes and lives in freshwater ponds and streams, gliding under stones and feeding on small animals.

Linear momentum stays constant only when no net external force acts. Linear momentum is the product of mass and velocity, p = mv.

Amphibians and most reptiles have a heart with three chambers: two atria and one ventricle. In frogs and toads, oxygen-rich blood from the lungs and oxygen-poor blood from the body both reach the single ventricle, so some mixing takes place.

Centrifugation separates very fine insoluble particles that are too small to settle on their own. The mixture is spun at high speed in a centrifuge.

Pearls are harvested from pearl oysters, which are bivalve molluscs. When a foreign particle, such as a grain of sand or a parasite, gets inside the shell, the oyster's mantle covers it layer after layer with nacre, the shiny material also called mother of pearl.

Faraday's law is a law of magnitude, not a direction rule. It states that the emf induced in a circuit is proportional to the rate at which the magnetic flux through it changes.

A galvanometer detects whether a small electric current is flowing in a circuit and shows its direction. A moving-coil galvanometer has a coil placed between the poles of a magnet.

Reverberation is the persistence of sound in a hall after the source has stopped, caused by repeated reflections from the walls, ceiling and floor.

This goes against the conservation of charge: the total charge of an isolated system always stays the same. Electric charge has three basic properties.

These two organelles carry their own circular DNA and their own small (70S) ribosomes, so they can make some of their own proteins.

This statement is false: enzymes are mostly proteins, but most proteins are not enzymes. Proteins do many jobs in the body.

Of the four, X-rays lie farthest towards the short-wavelength, high-energy end of the electromagnetic spectrum. All electromagnetic waves travel at the speed of light in vacuum but differ in wavelength.

Nuclear power plants produce energy by splitting heavy nuclei, and the energy released is given by Einstein's relation E = mc².

The time period of a simple pendulum depends on the square root of its length and not on its mass, so four times the length gives twice the period.

Antibodies are made by B lymphocytes, which turn into plasma cells that release antibodies in very large numbers during an immune response.