General Science Mixed Quiz: Set 24

The correct answer is D, violet. White light is a mixture of colours, and the refractive index of the glass of a prism is slightly different for each of them, being greatest for violet and least for red. A larger refractive index means a greater bending, so violet is deviated most and red least, and the colours spread out into the band called the spectrum, remembered as VIBGYOR from violet at the bottom to red at the top. This splitting is called dispersion.

Option A, red, has the longest wavelength of the visible colours and is bent the least, which is why it appears at the other end of the band. Options B and C, green and yellow, lie in the middle of the spectrum and are deviated by amounts between those of violet and red.

The correct answer is C, a and c, that is Spirulina and Chlorella. Both are tiny algae grown in tanks and sold as protein rich food supplements, and both have been studied as food for astronauts. Spirulina is a blue green alga, really a cyanobacterium, whose dried powder is about sixty per cent protein and also carries iron and beta carotene. Chlorella is a single celled green alga that multiplies very fast in a small space and gives off oxygen as it grows, which is why space agencies have tested it in closed life support systems. Such food from microbes is called single cell protein. Option A is wrong because Spirogyra, the slippery filamentous alga of ponds, is not eaten as a supplement. Option B is wrong for the same reason, as it also carries Spirogyra. Option D is wrong because it leaves out both correct names and adds Funaria, which is a moss and not an alga at all. Exam tip: Spirulina and Chlorella give single cell protein.

The correct answer is B, reflection of ultrasonic waves. SONAR stands for Sound Navigation and Ranging. A transmitter on the ship sends short ultrasonic pulses into the water, the pulses are reflected from the sea bed, a submarine, an iceberg or a shoal of fish, and a detector records the returning echo. Since the pulse travels down and back, the depth equals the speed of sound in water multiplied by the time taken and divided by two.

Option A is wrong because light is absorbed within a short distance in sea water and is useless for sounding the deep ocean. Option C is wrong for a similar reason, as radio waves are strongly attenuated in salt water, which is why submarines must surface or use very low frequencies to communicate. Option D names the wrong band and the wrong phenomenon: infrasound is below the audible range and interference is not how ranging is done.

The correct answer is B, tuberculosis (TB). The BCG vaccine takes its name from Albert Calmette and Camille Guerin, the two French scientists who developed it from a weakened strain of Mycobacterium bovis. In India it is given as a single dose soon after birth under the Universal Immunisation Programme, and it protects infants mainly from the severe forms of the disease, such as tuberculous meningitis and miliary tuberculosis. Tuberculosis itself is caused by the bacterium Mycobacterium tuberculosis, identified by Robert Koch in 1882, and it spreads through droplets when a patient coughs. Option A is wrong because typhoid, caused by Salmonella typhi, has its own conjugate vaccine. Option C is wrong because mumps is a viral disease covered by the MMR vaccine along with measles and rubella. Option D is wrong because plague, caused by Yersinia pestis and carried by rat fleas, needs a different vaccine. Exam tip: BCG at birth for TB, and World TB Day falls on 24 March.

The correct answer is C, 6000 ohm. By Ohm's law the resistance equals the potential difference divided by the current. Here the current must first be converted into the base unit: two milliampere is 0.002 ampere. Dividing twelve volt by 0.002 ampere gives six thousand ohm, that is six kilo-ohm.

Option A, 600 ohm, is what you get if the milliampere is mistaken for a hundredth of an ampere instead of a thousandth, a common slip under time pressure. Option B, 6 ohm, is the answer to a different question, namely twelve volt divided by two ampere, and it ignores the prefix milli altogether. Option D, 60 ohm, does not follow from the numbers at all and is there only to fill the choice. The lesson is to convert every prefix, milli, micro, kilo or mega, into the base unit before dividing.

The correct answer is B, Papaver Somniferum. Opium is the dried latex of the opium poppy, whose botanical name is Papaver somniferum; the second word means sleep bringing. The milky latex is collected by making shallow cuts in the unripe capsule, and from it come the medicines morphine and codeine, used to control pain and cough. India grows the crop only under licence from the Narcotics Commissioner at Gwalior in Madhya Pradesh, and the licensed districts lie in Madhya Pradesh, Rajasthan and Uttar Pradesh, which is why state papers ask this question. Option A is wrong because Emblica officinalis is amla, the Indian gooseberry, rich in vitamin C. Option C is wrong because Rauvolfia serpentina is sarpagandha, the source of reserpine used for high blood pressure. Option D is wrong because Cinchona species yield quinine, the old treatment for malaria. Exam tip: opium Papaver somniferum, amla Emblica officinalis, quinine from Cinchona.

The correct answer is C, 18. The capacity of a shell is given by the formula 2n squared, where n is the number of the shell counted outward from the nucleus. The M shell is the third, so its capacity is 2 multiplied by 3 squared, which is 18. Option A is wrong because 8 is the capacity of the L shell, the second, and is also the greatest number of electrons an outermost shell may hold, which is a different rule. Option B is wrong because 2 is the capacity of the K shell, the first and nearest to the nucleus. Option D is wrong because 32 is the capacity of the N shell, the fourth. Note that in an atom such as calcium the M shell stops at 8 because it is the outermost shell at that stage, which does not change its full capacity of 18.

The correct answer is A, a suspension is a heterogeneous mixture. In a suspension the particles of the solute are large enough to be seen and do not dissolve; they stay spread through the liquid only while it is stirred and settle to the bottom when it is left standing. Chalk powder in water, muddy river water and a shaken bottle of paint are everyday examples. Because the particles are big, a suspension scatters a beam of light, showing the Tyndall effect, and the particles can be separated by filtration. B is wrong because solids spread in a gas, such as smoke, are aerosols, a kind of colloid, not a suspension. C is wrong because the particles of a suspension are large enough to be seen with the naked eye; it is the particles of a solution that cannot be seen. D is wrong because a homogeneous mixture is a solution, which is uniform throughout. Exam tip: solution homogeneous, suspension heterogeneous and settles, colloid in between.

The correct answer is A, that meiosis doubles the number of chromosomes, because meiosis does the opposite. It is a reduction division: one parent cell with the full, diploid set gives four cells with half the number of chromosomes, the haploid set. That halving is what keeps the chromosome number of a species steady, since a sperm and an egg each bring half and the fertilised egg is back to the full number. The other three statements are true. It takes place in the gonads, the testes and the ovaries, to make gametes. It runs in two rounds, meiosis I and meiosis II, with only one copying of the DNA. And during meiosis I the chromosomes of the two parents exchange segments by crossing over, so the genes are mixed and no two gametes are alike. B, C and D are therefore not the answer. Exam tip: mitosis keeps the number, meiosis halves it.

The correct answer is C, Two. A normal umbilical cord contains two arteries and one vein, three blood vessels in all.

The umbilical cord joins the developing foetus to the placenta. The two umbilical arteries carry deoxygenated blood, carbon dioxide and wastes from the foetus to the placenta, while the single umbilical vein brings oxygen-rich blood and nutrients from the placenta back to the foetus. This is the reverse of the usual pattern in the body, where arteries carry oxygenated blood. The vessels are cushioned by a jelly-like tissue called Wharton's jelly, and a mature cord is about 50 to 55 cm long.

A is wrong: three is the total number of vessels, not of arteries. B is wrong: one is the number of umbilical veins. D is wrong: four vessels are never present in a normal cord.

Exam tip: Umbilical cord - two arteries plus one vein; the vein is the one carrying oxygenated blood to the foetus.

The correct answer is C, Respiration in presence of oxygen. Aerobic respiration is the breakdown of glucose in the presence of oxygen, giving carbon dioxide, water and a large amount of energy. It takes place mainly in the mitochondria, which is why they are called the powerhouse of the cell, and one molecule of glucose yields about 38 molecules of ATP. Anaerobic respiration, which happens without oxygen, releases far less energy: yeast converts glucose into ethanol and carbon dioxide, while our muscle cells during hard exercise form lactic acid, the cause of cramps. A is wrong because respiration without molecular oxygen is anaerobic respiration. B is wrong because breathing through the skin, as frogs do, is cutaneous respiration, a route for gas exchange rather than a type of cellular respiration. D is wrong because respiration through gills is branchial respiration, seen in fish. Exam tip: aerobic respiration means with oxygen, 38 ATP, in mitochondria.

The correct answer is B, H3O+. A hydrogen ion (H+) is just a bare proton, so it cannot stay alone in water. It at once attaches itself to a water molecule and forms the hydronium ion, H3O+. So when an acid such as hydrochloric acid dissolves in water, it really produces H3O+ ions, and these give the solution its acidic nature. Without water, acids do not show acidic behaviour, which is why dry HCl gas does not change the colour of dry blue litmus paper. Option A is wrong because HO- (OH-) is the hydroxide ion, which bases give in water. Option C is wrong because H2 is hydrogen gas, a neutral molecule, not an ion. Option D is wrong because H2SO4 is sulphuric acid itself, a compound that releases hydrogen ions in water. Exam tip: acids give H3O+ ions in water and bases give OH- ions; a solution with pH 7 is neutral, below 7 acidic and above 7 basic.

The correct answer is C, Glucose, water, salts and amino acids. Blood is filtered in the glomerulus of the nephron, and the filtrate that first enters the tubule still holds many useful substances. As it passes along the tubule these are taken back into the blood, a step called selective reabsorption, so that only waste and surplus water go on to form urine. Glucose, amino acids, most salts and a large part of the water are returned; how much water is taken back depends on how much the body needs and on how much dissolved waste has to be sent out. B and D are wrong because proteins are too large to pass the glomerular filter, so they never reach the filtrate and cannot be reabsorbed from it. A is wrong for the same reason applied to fats, which also do not appear in the filtrate. Exam tip: proteins and fats stay in the blood, glucose and amino acids are fully reabsorbed.

The correct answer is D, Sickle cell anaemia, Haemophilia, Down syndrome. All three are genetic disorders, caused by changes in genes or chromosomes and passed on through birth, not by germs. Sickle cell anaemia is an autosomal recessive disease in which a single change in the haemoglobin gene makes red blood cells sickle-shaped. Haemophilia is a sex-linked recessive disorder carried on the X chromosome, in which blood does not clot properly; it mostly affects males, and it is called the royal disease because it spread among Queen Victoria's descendants. Down syndrome is a chromosomal disorder caused by an extra copy of chromosome 21, also called trisomy 21. Option A is wrong because AIDS is caused by the HIV virus and is not inherited through genes. Option B is wrong because AIDS and Hepatitis B are viral infections, and most cancers come from mutations acquired during life. Option C is wrong because Hepatitis B is a viral infection, even though haemophilia and colour blindness are genetic. Exam tip: genetic disorders include sickle cell anaemia, haemophilia, colour blindness, thalassaemia and Down syndrome.

The correct answer is B, Neuron. Dendrites and the axon are the two kinds of processes that grow out of a neuron, the nerve cell that carries messages through the body. The cell body, also called the cyton, holds the nucleus. Dendrites are short branched fibres that pick up a signal and carry it towards the cell body, while the axon is a single long fibre that carries the signal away towards the next cell. The gap between the axon of one neuron and the dendrite of the next is the synapse, where a chemical crosses over. A neuron is the longest cell in the human body. A is wrong because a mature human red blood cell is a disc without a nucleus and only carries oxygen. C is wrong because the nephron is the filtering unit of the kidney, made of many cells, not a cell itself. D is wrong because white blood cells fight infection and move by changing shape. Exam tip: dendrite brings the signal in, axon takes it out, synapse joins two neurons.

The correct answer is D, gold. Calaverite is gold telluride, with the formula AuTe2.

It is one of the very few minerals in which gold occurs chemically combined rather than as the free metal, because gold is a noble metal that usually resists reaction. Calaverite was named after Calaveras County in California, where it was found in 1861, and it is an important gold ore in Kalgoorlie in Australia and in Cripple Creek in Colorado. It looks brassy yellow to silvery white and is brittle.

Option A is wrong because the common silver telluride is hessite, and silver's chief ore is argentite. Option B is wrong as zinc is mined mainly as zinc blende, a sulphide. Option C is wrong because copper comes largely from copper pyrites, malachite and cuprite.

Exam tip: link ore to metal - calaverite gold, argentite silver, zinc blende zinc, bauxite aluminium, haematite iron, cinnabar mercury.

The correct answer is C, Carotenoid. Carotenoids are the yellow, orange and red pigments inside the chloroplast that absorb sunlight and hand the energy on to chlorophyll, so they are the only choice here that traps light for photosynthesis. They come in two groups, the carotenes and the xanthophylls, and they also protect chlorophyll from damage by strong light. Because they lie hidden under the green of chlorophyll, they become visible in autumn leaves, in carrots and in ripe tomatoes. Option A is wrong because cristae are the folds of the inner membrane of the mitochondrion and belong to respiration, not photosynthesis. Option B is wrong because amyloplasts are colourless plastids that only store starch and have no pigment to absorb light. Option D is wrong because the vacuole is a sap filled sac that stores water and waste and keeps the cell firm. Exam tip: chlorophyll is the main photosynthetic pigment and carotenoids are the accessory pigments.

The correct answer is C, water bodies. Red algae, the division Rhodophyta, live in water, mostly in warm and shallow sea water, with a few species in fresh water. Their colour comes from the pigment phycoerythrin, which masks the green of chlorophyll and lets them use the blue light that reaches greater depths, so some grow deeper than other algae. Porphyra, Gracilaria and Polysiphonia are common examples, and the agar used in laboratories and the carrageenan used in food both come from this group. Coralline red algae deposit calcium carbonate and help build coral reefs. Option A is wrong because bare mountain slopes lack the standing water algae need. Option B is wrong because a city is a settlement, not a water body or habitat for marine algae. Option D is wrong because deserts are dry and an alga cannot complete its life cycle without water. Exam tip: Rhodophyta are red from phycoerythrin, Chlorophyta green from chlorophyll, Phaeophyta brown from fucoxanthin.

The correct answer is B, Rod-shaped. Bacteria are grouped by shape, and bacilli are the rod-shaped ones; the Latin word bacillus itself means a small rod or stick. Tuberculosis, tetanus, typhoid and anthrax are all caused by rod-shaped bacteria, and Lactobacillus, the bacterium that curdles milk into curd, belongs to the same group. The other shapes in this classification are cocci, which are spherical, spirilla, which are long and spiral, and vibrio, which are curved like a comma. A is wrong because comma-shaped bacteria are called vibrio, the best known being Vibrio cholerae, which causes cholera. C is wrong because spiral bacteria are spirilla and spirochaetes. D is wrong because spherical bacteria are cocci, such as Streptococcus. Exam tip: cocci are round, bacilli are rods, spirilla are spirals and vibrio are comma-shaped.

The correct answer is D, Ligament. A ligament is the connective tissue that joins one bone to another at a joint. It is very elastic and strong, and it holds the bones in place so that a joint can move without the bones slipping apart. Ligaments contain little matrix of their own and are stretched when a joint is twisted, which is what happens in a sprain. A is wrong because a tendon joins a muscle to a bone; tendons are fibrous and strong but have limited stretch, so the pull of a muscle is passed straight to the bone. B is wrong because cartilage is the smooth, flexible tissue that pads the ends of bones and shapes the nose and ear, cushioning the joint rather than tying the bones together. C is wrong because matrix is the material in which the cells of a connective tissue are embedded, not a structure by itself. Exam tip: ligament bone to bone, tendon muscle to bone.