General Science Previous Year Questions (PYQ) with Answers – Page 45

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

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

The English physicist James Prescott Joule showed around 1841 that when a current flows through a conductor, the heat produced is proportional to the square of the current, the resistance of the conductor and the time for which the current flows.

A plane mirror is a spherical mirror of infinite radius of curvature, so its focal length f = R/2 is also infinite.

Estrogen, made mainly by the ovaries, brings about the female secondary sexual characters at puberty. At puberty the pituitary releases FSH and LH, which stimulate the ovaries to secrete estrogen.

The human body conducts electricity because its fluids contain dissolved salts that break up into ions, and these ions carry current.

The word fission is used in two sciences: in biology for splitting of a single-celled organism, and in physics for splitting of a heavy nucleus.

A disease that stays constantly present at a steady baseline level in a particular area, without being brought in from outside, is called endemic.

Resistivity is a property of the material and its temperature, not of the wire's shape, so every copper wire has the same resistivity.

Iodine is a non-metal, yet its solid crystals have a shiny, metallic lustre, which makes it the standard exception taught in school chemistry.

Among the options it is the only vitamin made by bacteria; no plant or animal cell can make it, so bacteria, including those in the gut, are its source.

Cattle, buffaloes, goats and sheep are ruminants, and a ruminant's stomach has four chambers. The four chambers are the rumen, the reticulum, the omasum and the abomasum.

Power is the reciprocal of the focal length in metres, so P = 1 ÷ 0.25 m = +4 D. The power of a lens tells how strongly it converges or diverges light.

The cornea is a clear layer made of cells and proteins, chiefly collagen fibres laid out in a regular pattern that keeps it transparent.

Mass by mass percentage is the mass of solute divided by the mass of the whole solution: 20 ÷ (20 + 180) × 100 = 10%.

Silver reacts with sulphur compounds in the air, mainly hydrogen sulphide, and forms a black coating of silver sulphide. This blackening is the tarnishing of silver, a kind of corrosion.

Osmosis is the passage of water from where water is more concentrated (a dilute solution) to where it is less concentrated, across a membrane that lets water through but holds back solutes.

Cytokinins are the plant hormones whose main job is to promote cell division, or cytokinesis, which gives them their name.

Starlight is bent again and again as it passes through layers of air whose temperature and density keep changing, so the star seems to flicker in brightness and position.

Particles in a colloid are large enough to scatter a beam of light, which makes the path of the beam visible.