General Science Mixed Quiz: Set 99

The normal human ear hears sound from about 20 hertz to 20,000 hertz, the audible range. Frequency, measured in hertz, is the number of vibrations per second, and it decides the pitch of a sound: the higher the frequency, the shriller the note.

The de Broglie wavelength depends only on momentum, so equal wavelengths mean equal momenta. In 1924 Louis de Broglie proposed that every moving particle has a wave linked to it, with wavelength λ = h/p, where h is Planck's constant and p is the linear momentum.

Hedgehogs and pangolins curl into a tight ball when threatened, covering the soft belly and face with spines or scales; marmots do not.

Red biotechnology is the branch applied to medicine and health care, including the making of insulin, antibiotics and vaccines. Biotechnology is often divided by colour according to its field of use.

Cardiac muscle shows the cross stripes of skeletal muscle under the microscope, but it is not under the control of the will and it beats rhythmically on its own, driven by the pacemaker of the heart; its cells are branched and joined end to end by intercalated discs, which let…

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.

Colostrum is the thin yellowish milk secreted in the first days after delivery and is rich in antibodies, especially immunoglobulin A, which pass to the baby and protect it from infection at a stage when its own immune system is immature; this protection is called passive immunity.

Rotational kinetic energy is ½Iω², and the ring has the larger moment of inertia. For a thin ring about the axis through its centre and perpendicular to its plane, all the mass sits at distance R, so I = MR².

The red cells of group O carry neither the A antigen nor the B antigen, so when they are transfused the antibodies in the recipient's plasma find nothing to bind to and the cells are not destroyed, which is why group O, and strictly O negative, can be given to…

Marie Curie discovered radium; the first two pairs have their discoveries swapped. Marie Curie and Pierre Curie discovered the radioactive elements polonium and radium in 1898, and Marie Curie went on to win Nobel Prizes in both physics (1903) and chemistry (1911).

A restriction endonuclease recognises a short palindromic sequence in DNA and cuts both strands there, leaving sticky ends that can pair with another piece cut by the same enzyme; Hind II was the first such enzyme to be discovered and EcoRI from Escherichia coli is the most widely used.

Groundnut, horse-gram and soybean are all legumes of the family Fabaceae (Leguminosae), the pea family. Members of the pea family bear their seeds in pods and carry root nodules in which Rhizobium bacteria fix atmospheric nitrogen.

Lemongrass and its close relative citronella grass yield aromatic oils that keep mosquitoes away, so they are the base of many natural repellents.

Argon is an inert gas, so it does not react with the white-hot tungsten filament and slows its evaporation, which makes the bulb last longer.

A mixture of carbon monoxide and hydrogen is called synthesis gas, or syngas, because it is the starting material for making methanol and many other compounds.

Capra hircus is the scientific name of the domestic goat, in which Capra is the genus and hircus the species, written in the two-word form that Carl Linnaeus gave to biology.

X-rays are electromagnetic waves made of uncharged photons, so electric and magnetic fields cannot bend them. Electric and magnetic fields exert force only on charged particles: a charge q feels a force qE in an electric field and qvB in a magnetic field.

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.

To just complete a vertical circle, a bob on a string needs a speed of at least √(5gL) at the lowest point, and √(5 × 10 × 0.5) = √25 = 5 m/s. A string can only pull, never push.

Meiosis makes gametes that differ from one another, and fertilization joins a gamete from each of two parents, so every offspring gets a new mix of genes.