General Science Mixed Quiz: Set 92

Planck's constant has the dimensions [ML²T⁻¹], exactly those of angular momentum. From E = hf, h = E / f. Energy has dimensions [ML²T⁻²] and frequency has [T⁻¹], so h has [ML²T⁻²] ÷ [T⁻¹] = [ML²T⁻¹], with the SI unit joule-second.

Above the threshold, the kinetic energy of the ejected electrons rises as the frequency of the light rises, so the statement that it does not change is wrong.

A freely falling object moves with a uniform acceleration, the acceleration due to gravity, g, about 9.8 m/s² near the Earth's surface.

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.

The apple's gravitational potential energy first becomes kinetic energy as it falls, some is lost as heat to the air on the way, and at impact the rest goes into heating the ground and apple and into sound.

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.

The trapped steam raises the pressure inside the cooker, and at higher pressure water boils at a higher temperature, so food cooks faster.

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 focal length is 10 cm, and an object between F and C of a concave mirror gives a real image beyond C, in front of the mirror.

Together the two resins take out every dissolved ion, which leaves demineralised water. In the cation exchange resin (written RH), metal ions such as Ca2+, Mg2+ and Na+ are swapped for H+ ions.

Twenty crests and twenty troughs make twenty complete waves in 0.1 second, so the frequency is 200 Hz and the wavelength is 330 ÷ 200 = 1.65 m. One complete wave, or one cycle, contains one crest and one trough (for sound, one compression and one rarefaction).

Jupiter is a planet; it does not make its own light and shines only by reflecting sunlight. A luminous object produces light of its own, as stars do by nuclear fusion in their cores, where hydrogen is turned into helium.

Putting a soft iron bar inside a solenoid makes the magnetic field much stronger, so the claim that the field stays the same is not correct.

Abscisic acid is the one plant hormone in this list that slows growth instead of speeding it up, which is why it is often called the stress hormone of plants.

Atoms get smaller along a period and larger down a group. Moving from left to right in a period, electrons are added to the same shell while the nuclear charge rises by one at each step.

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).

The nitride ion, N³⁻, carries a charge of minus three, so its valency is -3. Nitrogen has five electrons in its outer shell.

Walls are whitewashed with a solution of slaked lime, calcium hydroxide, which is an inorganic compound; quicklime itself is not applied, and the shiny layer comes from Ca(OH)₂, not CaO.

Gold is a noble metal at the bottom of the reactivity series, so it does not react with oxygen, water or ordinary acids.

Cyclohexane, C 6 H 12, has 6 C–C single bonds and 12 C–H single bonds, 18 single bonds in all and no double or triple bond.