Physics GK Quiz-4

Physics GK Quiz-4

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

    61. A particle dropped from the top of a tower uniformly falls on ground at a distance which is equal to the height of tower. Which of the following paths will be traversed by the particle ?

    (1) Circle 
    (2) Parabolic
    (3) Great circle
    (4) Hyper–parabolic
    Answer:
    61. (2) If a particle dropped from the top of a tower uniformly falls on ground at a distance which is equal to the height of tower then a parabolic path will be traversed by a particle because when the particle is dropped that point is called the point of projection and when it reaches the ground that point is called the point of impact. Now, if the two points is met with one another the curve emerges is parabolic in nature. Hence, we can say that the path followed by the particle is of parabolic trajectories.

    62. Electron microscope was invented by

    (1) Knoll and Ruska
    (2) Robert Koch
    (3) Leeuwenhock
    (4) C.P. Swanson
    Answer:
    62. (1) It is widely accepted that the first prototype of an electron microscope was built by Ernst Ruska and Max Knoll in 1931; it was not more powerful than an optical microscope, but it demonstrated the principle that is still used in today’s sophisticated and powerful instruments, and earned its builders a share of a Nobel Prize. 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.

    63. When a bottle of scent is kept open in a corner of a room its odour is felt in all parts of the room. This is due to the phenomenon of :

    (1) evaporation 
    (2) vaporisation
    (3) diffusion 
    (4) sublimation
    Answer:
    63. (3) Diffusion is one of several transport phenomena that occur in nature. A distinguis-hing feature of diffusion is that it results in mixing or mass transport without requiring bulk motion. Thus, diffusion should not be confused with convection or advection, which are other transport mechanisms that use bulk motion to move particles from one place to another. From the atomistic point of view, diffusion is considered as a result of the random walk of the diffusing particles. In molecular diffusion, the moving molecules are self-propelled by thermal energy.

    64. Clear nights are colder than cloudy nights because of

    (1) conduction
    (2) condensation
    (3) radiation
    (4) insolation
    Answer:
    64. (3) Cloudless nights are colder because the nights that have clouds provide a blanket for the earth and trap some of the hot day air where as the cloudless nights have no protection so all the hot air rises up into the sky. radiation is a process in which energetic particles or energetic waves travel through vacuum, or through matter-containing media that are not required for their propagation. Waves of a massive medium itself, such as water waves or sound waves, are usually not considered to be forms of “radiation” in this sense. By contrast, gravitational waves, which are waves of space-time itself, qualify as a type of radiation.

    65. Speed of sound is the greatest in :

    (1) Water 
    (2) Air
    (3) Glass 
    (4) Glycerine
    Answer:
    65. (3) Sound travels faster in liquids and non-porous solids than it does in air. It travels about 4.3 times
    as fast in water (1,484 m/s), and nearly 15 times as fast in iron (5,120 m/s), than in air at 20 degrees
    Celsius. Sound waves in solids are composed of compression waves (just as in gases and liquids), but also exhibit a different type of sound wave called a shear wave, which occurs only in solids. The speed
    of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic
    medium. In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s). This
    is 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds or approximately one
    mile in five seconds.

    66. A gas thermometer is more sensitive than a liquid thermometer because a gas :

    (1) is lighter than liquid
    (2) expands more than a liquid
    (3) is easy to obtain
    (4) does not change state easily
    Answer:
    66. (4) Gas is easily compressed so it would have a more versatile range of measurement at least in our
    atmospheric conditions. Liquid is not so easily compressed, so, very little pressure via mass w/gravity or heat would cause it to quickly jump between changes. A gas thermometer measures temperature by the variation in volume or pressure of a gas. One common apparatus is a constant volume thermometer.
    Gas thermometers are often used to calibrate other thermometers.

    67. Which one of the following is used for sun glasses ?

    (1) Pyrex glass
    (2) Flint glass
    (3) Crooks glass
    (4) Crystal glass
    Answer:
    67. (3) A type of glass that contains cerium and other rare earths and has a high absorption of ultraviolet
    radiation is used in sunglasses. Sunglasses or sun glasses are a form of protective eyewear designed
    primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are coloured, polarized or darkened. In the early 20th century they were also known as sun cheaters. The colour of the lens can vary depending on style, fashion, and purpose, but for general use, red, grey, green, or brown are recommended to avoid or minimize colour distortion, which could affect safety when, for instance, driving a car or a school bus.

    68. The speed of light with the rise in the temperature of the medium :

    (1) Increases
    (2) Decreases
    (3) Remains unaltered
    (4) Drops suddenly
    Answer:
    68. (3) The speed of light with the rise in the temperature of the medium remains unaltered because speed of light doesn’t depend on temperature. It does depend, however, on the refractive index of the substance it is travelling through. The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact because the length of the metre is defined from this constant and the international standard for time. The speed at which light propagates through transparent materials, such as glass or air, is less than c.

    69. Clothes keep us warm in winter because they :

    (1) supply heat
    (2) do not radiate heat
    (3) prevent air from contacting the body
    (4) prevent the heat of the body from escaping
    Answer:
    69. (4) 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. Hence, all the heat from our body gets trapped inside the clothes which makes us feels warmer with the clothes.

    70. In a refrigerator what produces the cooling ?

    (1) The ice which deposits on the freezer
    (2) The sudden expansion of a compressed gas
    (3) The evaporation of a volatile liquid
    (4) None of these
    Answer:
    70. (4) Basically, refrigeration system consists of devices that compress and expand refrigerant gas . When refrigerant gas is compressed it expels heat and when it is suddenly expanded, absorbs heat. A refrigerator (colloquially fridge) is a common household appliance that consists of a thermally insulated compartment and a heat pump (mechanical, electronic, or chemical) that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room. A vapor compression cycle is used in most household refrigerators, refrigerator– freezers and freezers. In this cycle, a circulating refrigerant such as R134a enters a compressor as low-pressure vapor at or slightly above the temperature of the refrigerator interior. The vapor is compressed and exits the compressor as highpressure superheated vapor. The superheated vapor travels under pressure through coils or tubes comprising the condenser, which are passively cooled by exposure to air in the room. The condenser cools the vapor, which liquefies. As the refrigerant leaves the condenser, it is still under pressure but is now only slightly above room temperature. This liquid refrigerant is forced through a metering or throttling device, also known as an expansion valve (essentially a pin-hole sized constriction in the tubing) to an area of much lower pressure.

    71. Why are we able to hear short wave broadcasts better than long wave broadcasts ?

    (1) Short waves are more energetic than long waves.
    (2) Short waves are unaffected by atmospheric disturbances.
    (3) Short wave broadcasts are made by nearby radio stations.
    (4) By convention, short waves are meant for long distances, whereas long waves are reserved for short distances.
    Answer:
    71. (1) Shortwave radio is used for broadcasting of voice and music, and long-distance communication to ships and aircraft, or to remote areas out of reach of wired communication or other radio services and that’s why it is more energetic than long waves. Shortwave radio is radio communication using the upper MF (medium frequency) and all of the HF (high frequency) portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m (1500 kHz) which marked the original upper limit of the medium frequency band first used for radio communications. The broadcast medium wave band now extends above the 200 m/1500 kHz limit, and the amateur radio 1.8 MHz – 2.0 MHz band (known as the “top band”) is the lowest-frequency band considered to be ‘shortwave’.

    72. When the barometer reading dips suddenly, it is an indication of

    (1) Hot weather
    (2) Calm weather
    (3) Storm
    (4) Dry weather
    Answer:
    72. (3) Sudden and great fluctuations of the barometer at any time of the year indicate unsettled weather for several days, perhaps a fortnight. If the barometer falls two or three-tenths of an inch in four hours,
    one can expect a gale of wind. If the surface of the mercury in the cistern of the barometer vibrates upon the approach of a storm, the gale can be expected to be severe. 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.

    73. Good conductor of electricity is

    (1) dry air 
    (2) paper
    (3) kerosene 
    (4) graphite
    Answer:
    73. (4) Graphite has a tendency to behave very much like a metal because the carbon molecules arrange
    themselves into a lattice structure. The crystal lattice is the same orientation that metal forms, and it allows the free-movement of electrons, making it a good electrical conductor. The characteristics possesses by the graphite for conduction is far better than the dry air paper and kerosene and that’s what makes it a good conductor.

    74. Which of the following is a nonrenewable source of energy ?

    (1) Biogas 
    (2) Solar
    (3) Wind 
    (4) Coal
    Answer:
    74. (4) A non-renewable resource is a natural resource which cannot be reproduced, grown, generated, or used on a scale which can sustain its consumption rate. So, coal is non-renewable source of energy. Once it is depleted, there is no more available for future needs. Fossil fuels (such as coal, petroleum, and natural gas), nuclear power (uranium) and certain aquifers are examples of non-renewable resources. In contrast, resources such as timber (when harvested sustainably) and wind (used to power
    energy conversion systems) are considered renewable resources. Natural resources such as coal, petroleum (crude oil) and natural gas take thousands of years to form naturally and cannot be replaced as fast as they are being consumed.

    75. Solar energy is converted into chemical energy during

    (1) Transpiration
    (2) Photosynthesis
    (3) Diffusion
    (4) Osmosis
    Answer:
    75. (2) In photosynthesis, solar energy is converted to chemical energy. The chemical energy is stored in the form of glucose (sugar). Carbon dioxide, water, and sunlight are used to produce glucose, oxygen, and water. Photosynthesis is a process used by plants and other organisms to convert the light energy captured from the sun into chemical energy that can be used to fuel the organism’s activities.
    Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic
    organisms are called photo-autotrophs, since they can create their own food. In plants, algae, and
    cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product.
    Photosynthesis is vital for all aerobic life on Earth.

    76. The term ‘equinox’ means

    (1) The path which the Earth takes around the Sun
    (2) The axis of the Earth around which it rotates
    (3) When the day and night are of equal duration
    (4) The time when the Sun seems to be going round and round in the sky in the Arctic but does not go below the horizon
    Answer:
    76. (3) The name “equinox” is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day have approximately equal length. An equinox occurs twice a year (around 20 March and 22 September), when the tilt of the Earth’s axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth’s equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The equinoxes are the only times when the sub-solar point is on the Equator. This point (the place on the Earth’s surface where the center of the Sun can be observed exactly overhead) crosses the Equator moving northward at the March equinox and crosses the Equator moving southward at the September equinox.

    77. Heat from the Sun reaches the Earth by

    (1) Reflection 
    (2) Conduction
    (3) Radiation 
    (4) Convection
    Answer:
    77. (3) The radiation (light, heat, etc.) travels through the intervening 150, 000,000 kilometers in 8 minutes. Radiation is a process in which energetic particles or energetic waves travel through vacuum, or through matter-containing media that are not required for their propagation. Waves of a massive medium itself, such as water waves or sound waves, are usually not considered to be forms of “radiation” in this sense. By contrast, gravitational waves, which are waves of space-time itself, qualify as a type of radiation. By contrast, most non-ionizing radiation is harmful to organisms only in proportion to the thermal energy deposited, and is conventionally considered harmless at low powers which do not produce significant temperature rise.

    78. In which of the following cases, kinetic energy is being used in performing work ?

    (1) Paddling the bicycle to cover a distance
    (2) Driving a car to cover a distance
    (3) Wind mill grinding wheat grain
    (4) Rowing a boat in the lake
    Answer:
    78. (2) The work done on any object goes into changing the kinetic energy of that object. Since the work done by the car engine is equal to the change in kinetic energy of the car we can say that kinetic energy is being used in performing work. The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.

    79. Which of the following parts of the sunlight makes the solar cooker hot ?

    (1) Ultra violet 
    (2) Red light
    (3) Infra red 
    (4) Cosmic rays
    Answer:
    79. (3) Glass transmits visible light but blocks infrared thermal radiation from escaping. This amplifies the heat trapping effect. A solar cooker, or solar oven, is a device which uses the energy of direct sunlight to heat food or drink to cook it or sterilize it. The vast majority of the solar cookers presently in use are relatively cheap, low-tech devices. Because they use no fuel and cost nothing to operate, many nonprofit organizations are promoting their use worldwide to help reduce fuel costs for low-income people, reduce air pollution and slow deforestation and desertification, caused by use of firewood for cooking. Solar cooking is a form of outdoor cooking and is often used in situations where minimal fuel
    consumption is important, or the danger of accidental fires is high.

    80. If the velocity-time graph of a particle is represented by y = mt + c, then the particle is moving with

    (1) constant speed
    (2) constant velocity
    (3) constant acceleration
    (4) varying acceleration
    Answer:
    80. (3) In this case the given equation shows that that the velocity is linear with time and therefore the
    particle is moving with constant acceleration because for a particle to acquire constant acceleration the
    graph of the velocity time graph should be in linear with the time function.

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