Physics GK Quiz-3

Physics GK Quiz-3

Physics Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Physics for competitive examinations.

    41. Gamma rays can cause

    (1) gene mutation
    (2) sneezing
    (3) burning 
    (4) fever
    41. (1) In molecular biology and genetics, mutations are accidental changes in a genomic sequence of DNA: the DNA sequence of a cell’s genome or the DNA or RNA sequence in some viruses. These random sequences can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that occur during meiosis or DNA replication. Two nucleotide bases in DNA – cytosine and thymine – are most vulnerable to radiation that can change their properties. UV light can induce adjacent pyrimidine bases in a DNA strand to become covalently joined as a pyrimidine dimer.

    42. The substance which conducts current in the solid state is

    (1) diamond 
    (2) graphite
    (3) iodine
    (4) sodium chloride
    42. (2) The structure of graphite is unlike most other network substances. It is formed in ‘sheets’ of carbon atoms, each of which is bonded to only three others. The fourth valence electron of the carbon atom is delocalized and can move between the different layers, therefore carrying an electrical charge through the network of carbon atoms, a conductor is a material which contains movable electric charges. Unlike diamond (another carbon allotrope), graphite is an electrical conductor, a semimetal. It is, consequently, useful in such applications as arc lamp electrodes. Graphite is the most stable form of carbon under standard conditions. Therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds.

    43. Which set of conditions represents the easiest way to liquify a gas ?

    (1) Low temperature and high pressure
    (2) High temperature and low pressure
    (3) Low temperature and low pressure
    (4) High temperature and high pressure
    43. (1) Low temperature and high pressure set of conditions represents the easiest way to liquefy a
    gas. Liquefaction of gases is physical conversion of a gas into a liquid state (condensation). The processes are used for scientific, industrial and commercial purposes. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide, require pressurization as well. Liquefaction is used for analyzing the fundamental properties of gas molecules
    (intermolecular forces), for storage of gases. The liquefaction of gases is a complicated process that
    uses various compressions and expansions to achieve high pressures and very low temperatures, using,
    for example, turbo-expanders.

    44. What is colour of light related to ?

    (1) Amplitude 
    (2) Frequency
    (3) Quality 
    (4) Velocity
    44. (1) Colour or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue, and others. Colour derives from the spectrum of light (distribution of light power versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Colour categories and physical specifications of colour are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra. By defining a colour space, colours can be identified numerically by their coordinates.

    45. What principle/law explains the working of the hydraulic brakes in automobiles ?

    (1) Bernoulli’s law
    (2) Posieulle’s principle
    (3) Pascal’s law
    (4) Archimedes’ principle
    45. (3) Hydraulic brakes work on the principle of Pascal’s law which states that “pressure at a point in a fluid is equal in all directions in space”. According to this law when pressure is applied on a fluid it travels equally in all directions so that uniform braking action is applied on all four wheels. The hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing ethylene glycol, to transfer pressure from the controlling unit, which is usually near the operator of the vehicle, to the actual brake mechanism, which is usually at or near the wheel of the vehicle.

    46. The best conductor of heat among the following is

    (1) alcohol 
    (2) mercury
    (3) ether 
    (4) water
    46. (2) Since mercury is 13+ times as dense as water, a given volume of mercury would carry about 4.4 times as much heat, so mercury is best conductor of heat among the given options. It is the only metal that is liquid at standard conditions for temperature and pressure. Mercury has one of the narrowest ranges of its liquid state of any metal. Mercury is used in thermometers, barometers, manometers,
    sphygmomanometers, float valves, mercury switches, It is used in lighting: electricity passed through
    mercury vapor in a fluorescent lamp produces shortwave ultraviolet light which then causes the phosphor in the tube to fluoresce, making visible light.

    47. What is viewed through an electron microscope?

    (1) Electrons and other elementary particles
    (2) Structure of bacteria and viruses
    (3) Inside of human stomach
    (4) Inside of the human eye
    47. (2) Electron microscopes are used to observe a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, metals, and crystals. An electron microscope uses a beam of electrons to illuminate a specimen and produce a magnified image. An electron microscope (EM) has greater resolving power than a light-powered optical microscope because electrons have wavelengths about 100,000 times shorter than visible light photons. The electron microscope uses electrostatic and electromagnetic “lenses” to control the electron beam and focus it to form an image. Industrially, the electron microscope is often used for quality control and failure analysis.

    48. What apparatus is used to locate a submerged object?

    (1) Radar 
    (2) Sonar
    (3) Quasar 
    (4) Pulsar
    48. (2) Sonar (originally an acronym for Sound Navigation And Ranging) is a technique that uses sound
    propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect
    objects on or under the surface of the water, such as other vessels. Two types of technology share the name “sonar”: passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of “targets” in the water.

    49. The instrument which uses sound waves to measure the depth of oceans is

    (1) Radar 
    (2) Sonar
    (3) Altimeter 
    (4) Venturimeter
    49. (2) The instrument which uses sound waves to measure the depth of oceans is sonar. Sound waves
    can travel much faster from one point to another. Sound waves are far more accurate for measuring
    these vast distances. Sonar may be used as a means of acoustic location and of measurement of the echo
    characteristics of “targets” in the water. Sonar may also be used in air for robot navigation, and SODAR
    is used for atmospheric investigations.

    50. Which combination of colour is the most convenient during day and night time ?

    (1) Organe and blue
    (2) White and black
    (3) Yellow and blue
    (4) Red and green
    50. (4) Red and green is the most convenient combination during day and night time because of very precise visibility. In modern colour theory, also known as the RGB colour model, red, green and blue are additive primary colours. Red, green and blue light combined together makes white light, and these three colours, combined in different mixtures, can produce almost any colour. This is the principle used to make the colours on computer screen and television. The sRGB number of pure red, for example, is 255, 00, 00, which means the red component is at maximum intensity, and there is no green or blue. The sRGB number for crimson is 220, 20, 60, which means that the red is slightly less intense and therefore darker, there is some green, which leans it toward orange; and there is a larger amount of blue, which makes it slightly blue-violet.

    51. The instrument that measures and records the relative humidity of air is

    (1) Hydrometer 
    (2) Hygrometer
    (3) Lactometer 
    (4) Barometer
    51. (2) A hygrometer is an instrument used for measuring the moisture content in the environment. Humidity measurement instruments usually rely on measurements of some other quantity such as
    temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use temperature of condensation, or changes in electrical capacitance or resistance to measure humidity changes. Besides greenhouses and industrial spaces, hygrometers are
    also used in some incubators (egg), saunas, humidors and museums.

    52. The shape of our milky way galaxy is

    (1) circular 
    (2) elliptical
    (3) spiral
    (4) None of the above
    52. (3) The Milky Way is a barred spiral galaxy 100,000– 120,000 light-years in diameter containing 200–400 billion stars. It may contain at least as many planets, with an estimated 10 billion of those orbiting in the habitable zone of their parent stars. The Milky Way is the galaxy that contains our Solar System. This name derives from its appearance as a dim “milky” glowing band arching across the night sky, in which the naked eye cannot distinguish individual stars.

    53. The different colours of different stars are due to the variation of

    (1) temperature
    (2) pressure
    (3) density
    (4) radiation from them
    53. (1).Shortly after blackbody radiation was understood, it was noticed that the spectra of stars look extremely similar to blackbody radiation curves of various temperatures, ranging from a few thousand Kelvin to ~50,000 Kelvin. The obvious conclusion is that stars are similar to blackbodies, and that the colour variation of stars is a direct consequence of their surface temperatures.

    54. The fundamental scientific principle in the operation of battery is

    (1) acid-base interaction
    (2) dialysis
    (3) dissociation of electrolytes
    (4) oxidation-reduction
    54. (3) The electrolyte consists of a solvent (water, an organic liquid, or even a solid) and one or more
    chemicals that dissociate into ions in the solvent. These ions serve to deliver electrons and chemical matter through the cell interior to balance the flow of electric current outside the cell during cell operation. An electrolyte is a liquid or gel that contains ions and can be decomposed by electrolysis, e.g., that present in a battery. Commonly, electrolytes are solutions of acids, bases, or salts. Electrolyte solutions can also result from the dissolution of some biological (e.g., DNA, polypeptides) and synthetic polymers (e.g., polystyrene sulfonate), termed poly-electrolytes, which contain charged functional groups.

    55. Instrument used to measure the force and velocity of the wind is

    (1) Ammeter 
    (2) Anemometer
    (3) Altimeter 
    (4) Audiometer
    55. (2) An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics. Anemometers can be divided into two classes: those that measure the wind’s speed, and those that measure the wind’s pressure; but as there is a close connection between the pressure and the speed, an anemometer designed for one will give information about both.

    56. Wollen clothes keep the body warm because

    (1) Wool increases the temperature of the body
    (2) Wool is a bad conductor
    (3) Wool absorbs radiant heat from outer objects
    (4) Wool rejects heat from the outer objects
    56. (2) It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. Air reduces heat loss because it is an insulator or poor conductor of heat. Wool has several qualities that distinguish it from hair or fur: it is crimped, it is elastic, and it grows in staples
    (clusters).Wool’s scaling and crimp make it easier to spin the fleece by helping the individual fibers attach to each other, so they stay together. Because of the crimp, wool fabrics have a greater bulk than other textiles, and retain air, which causes the product to retain heat.

    57. If the length of a simple pendulum is halved then its period of oscillation is

    (1) doubled
    (2) halved
    (3) increased by a factor 2
    (4) decreased by a factor 2
    57. (4) The time period ‘T’ of a simple pendulum is given by T = 2p 1 g , where l is the length and g is the acceleration due to gravity. Let us suppose g be to be a constant, then T = 2 1 p . So the time period of a pendulum is directly proportional to the square root of its length. So, if the length increases, its time period also increase. It means that it takes longer to complete one oscillation. So when its length is halved, its time period is decreased by a factor of 2 .

    58. Mist is caused by

    (1) dry ice
    (2) ice at low temperature
    (3) water vapour at low temperature
    (4) carbon-monoxide in solid form
    58. (3) Mist is a phenomenon caused by small droplets of water suspended in air. It can occur as part of
    natural weather or volcanic activity, and is common in cold air above warmer water, in exhaled air in the cold, and in a steam room of a sauna. It can also be created artificially with aerosol canisters if the
    humidity conditions are right. The only difference between mist and fog is visibility. Mist usually occurs near the shores, and is often associated with fog. Mist can be as high as mountain tops when extreme temperatures are low. Freezing mist is similar to freezing fog, only the density is less and the visibility greater.

    59. While catching a ball, a player pulls down his hands to lower the–

    (1) force 
    (2) momentum
    (3) impulse 
    (4) catching time
    59. (2) A cricketer lowers his hands while taking a catch to decrease the rate of momentum. Cricketers
    increase the time by pulling their hand’s backward with the ball while taking a catch. Linear momentum
    or translational momentum is the product of the mass and velocity of an object. For example, a heavy truck moving fast has a large momentum—it takes a large and prolonged force to get the truck up to this speed, and it takes a large and prolonged force to bring it to a stop afterwards. If the truck were lighter, or moving slower, then it would have less momentum.

    60. When a barometer reading suddenly recedes, it indicates that climate–

    (1) will be very warm
    (2) will be extremely stormy
    (3) will remain cold
    (4) incessant rain for at least 48 hours
    60. (2) In summer, when the barometer falls suddenly, a thunderstorm can be expected, and if it does not rise again upon its cessation, the weather will probably continue unsettled for several days. In
    summer, when a thunderstorm happens, there is little or no depression of the barometer.

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