General Science Mixed Quiz: Set 192

Refractive index is the ratio of the speed of light in air to its speed in the medium, so the speed in glass is c divided by 3/2, which is (2/3)c. The absolute refractive index of a medium is n = c/v, where c is the speed of light in…

The correct answer is D, castor, which is the host of the eri silkworm and has nothing to do with lac culture.

Each half of the wire has a resistance of 10 Ω, and two 10 Ω resistors in parallel give 5 Ω. The resistance of a wire is R = ρL/A, so it is directly proportional to its length when the material and thickness stay the same.

The restoring force on the bob is mg sin θ. For small angles sin θ is almost equal to θ, so the force becomes proportional to the displacement and points back towards the mean position.

Chemical reactions involve only the outer, or valence, electrons, so these decide how an element behaves. Atoms combine by losing, gaining or sharing their valence electrons to reach a stable arrangement, usually eight electrons in the outer shell.

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.

Animal cells are bounded only by a flexible plasma membrane and have no rigid cell wall outside it. A cell wall is found in plants, where it is made mainly of cellulose, in fungi, where it is made of chitin, and in bacteria, where it is made of peptidoglycan.

Egg white is mostly water and protein, and heat denatures these proteins so that they set into an opaque white solid.

Pepsin works in the strongly acidic stomach, while trypsin works in the mildly alkaline small intestine. Pepsin is secreted by the chief cells of the stomach as inactive pepsinogen, which hydrochloric acid from the parietal cells turns into pepsin.

One kilowatt hour is 3.6 × 10⁶ joule, so 5.5 kWh = 5.5 × 3.6 × 10⁶ = 19.8 × 10⁶ joule.

The human brain has three main parts: the fore-brain, the mid-brain and the hind-brain. The hind-brain consists of the pons, the medulla and the cerebellum.

Weight equals mass times the acceleration due to gravity, and the acceleration due to gravity on the moon is about one-sixth of its value on the earth because the moon has a much smaller mass and a smaller radius.

Lactose, the sugar of milk, is a disaccharide formed when one molecule of glucose joins one molecule of galactose. Disaccharides are sugars made of two simple sugar units, or monosaccharides, linked by a glycosidic bond.

Adrenaline, released by the adrenal glands into the blood, speeds up the heart beat when the body faces stress or danger.

Soap micelles are large enough to scatter the light passing through the solution, and this scattering makes soapy water look cloudy.

Milk contains very little vitamin C, and what little there is gets destroyed further when milk is boiled. Milk is otherwise called a nearly complete food: it gives calcium and phosphorus for bones and teeth, good-quality protein, mainly casein, the sugar lactose, fat, and vitamins A, B2 and B12.

Two miscible liquids that form a homogeneous mixture are separated by distillation, which uses the difference in their boiling points.

The packet’s density is 800 g divided by 1,000 cm³, which is 0.8 g/cm³, less than the density of both liquids.

For lenses in contact the powers simply add, and here they are +2 D and +4 D. The power of a lens is the reciprocal of its focal length in metres, P = 1/f, and its unit is the dioptre.

A solar cell turns the energy of sunlight directly into electricity through the photovoltaic effect. A solar cell is a large p-n junction, usually made of silicon.