General Science GK Questions with Answers – Page 38

The nucellus is the diploid tissue of the ovule itself, while the synergids, the egg and the antipodals are haploid cells of the embryo sac.

The base is made thin and lightly doped so that most charge carriers from the emitter cross it to the collector.

Flint glass contains lead oxide, which gives it a high refractive index and clarity, so it is used for lenses and prisms of optical instruments.

Lysosomes bud off from the Golgi apparatus as small membrane-bound sacs packed with digestive enzymes. The hydrolytic enzymes of a lysosome are first made on ribosomes attached to the rough endoplasmic reticulum.

For resistors in parallel the reciprocals add: 1/11 + 1/22 + 1/33 = 11/66 = 1/6, so the equivalent resistance is 6 Ω. Taking 66 as the common denominator, 1/11 becomes 6/66, 1/22 becomes 3/66 and 1/33 becomes 2/66.

Rhizopus, the bread mould, feeds on dead and decaying organic matter, which is exactly what a saprophyte does. A saprophyte gets its food by releasing digestive enzymes onto dead matter such as stale bread, fruit or leaf litter and then absorbing the simple nutrients that result.

When natural gas or heavy oil burns with too little air, the carbon cannot all turn into carbon dioxide and separates as a very fine black soot, which is collected as carbon black.

Hydrated oxalic acid has a molar mass of 126 and is a dibasic acid, so its equivalent weight is 126 ÷ 2 = 63.

Iodine exists as diatomic molecules, I₂, in which two iodine atoms share a pair of electrons; so its atomicity is two, not one.

Here water only combines with calcium sulphate hemihydrate to form gypsum; no gas is given off and the paste simply sets hard.

Most carbon compounds are poor conductors of electricity, because their atoms are joined by covalent bonds and they do not form ions or free electrons that could carry a current.

Goldsmiths dip gold and silver ornaments in dilute nitric acid to dissolve the dirt, oxide layers and traces of base metals stuck to them, which brings back their shine.

Both statements are true, and the second explains the first: infrared waves are called heat waves because water molecules, present in most materials, absorb them readily and heat up.

Heat is energy in transit: it flows from a hotter body to a colder one only because their temperatures differ, and stops when they reach the same temperature.

The SI unit of inductance is the henry, symbol H, named after the American scientist Joseph Henry. Inductance measures how strongly a coil opposes a change in the current through it by producing an induced emf.

Plaster of Paris is calcium sulphate hemihydrate, CaSO₄·½H₂O, so one molecule of water is shared by two formula units of calcium sulphate, written (CaSO₄)₂·H₂O. It is made by heating gypsum, CaSO₄·2H₂O, to about 373 K (100 °C), when gypsum loses one and a half molecules of water per formula unit.

In the order visible light → ultraviolet → X-rays, the wavelength falls and the photon energy rises, so statements 1 and 2 are true and 3 is false.

In 1905 Einstein explained the photoelectric effect by treating light as made of packets of energy, later called photons, and he received the 1921 Nobel Prize in Physics for this work.

Light inside an optical fibre strikes the wall at more than the critical angle, is totally reflected back inside, and repeats this again and again along the fibre.

Fly ash is the fine powdery residue left after coal is burnt in thermal power stations; it is a mixture of oxides, not a pure form of carbon.