Physics GK Quiz-28

Physics GK Quiz-28

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

    541. The wavelength at which the peak of intensity of blackbody radiation occurs

    (1) increases with increase in temperature
    (2) decreases with increase in temperature
    (3) is the same at all temperatures
    (4) does not follow any pattern as temperature changes
    Answer:
    541. (2) According to Wien’s displacement law, when the temperature of a blackbody radiator increases, the overall radiated energy increases. Wavelength of maximum emission from a blackbody is inversely proportional to its temperature. Shorter-wavelength (higher-frequency) light corresponds to higher-energy photons.

    542. Man perceives sound vibrations in the frequency ranges of

    (1) 0 – 5 Hz 
    (2) 6 – 10 Hz
    (3) 11 – 15 Hz
    (4) 20 – 20000 Hz
    Answer:
    542. (4) The frequencies at which a human being can perceive sound vary between 20 Hertz and 20,000
    Hertz. It is within these frequency ranges that people can communicate to each other and listen to music.

    543. Certain substances loose their electrical resistance completely at super low temperature. Such substances are called.

    (1) Super conductors
    (2) Semi conductors
    (3) Dielectrics
    (4) Perfect conductors
    Answer:
    543. (1) Superconductors are materials that carry electrical current with little or no resistance when cooled below a certain temperature. While conventional superconductors need to be cooled close to absolute zero (-273.15 °C) before they superconduct, high temperature superconductors do so above the boiling point of liquid nitrogen (-196 °C).

    544. A metal ball and a rubber ball, both having the same mass, strike a wall normally with the same velocity. The rubber ball rebounds and the metal ball does not rebound. It can be concluded that

    (1) The rubber ball suffers greater change in momentum
    (2) The metal ball suffers greater change in momentum
    (3) Both suffer the same change in momentum
    (4) The initial momentum of the rubber ball is greater than that of the metal ball
    Answer:
    544. (1) As per the question, the rubber ball rebounds while the metal ball does not. So if m and v be the mass and velocity respectively, the change in momentum of rubber ball = 2 mv (in magnitude)
    However, the change in momentum of the metal ball = mv The rubber ball suffers almost twice the change in momentum as experienced by the metal ball.

    545. The oil in the wick of lamp rises due to

    (1) Pressure difference
    (2) Pheonomenon of capillarity
    (3) Low viscosity of oil
    (4) Force of cohesion
    Answer:
    545. (2) The oil in the wick of lamp rises due to phenomenon of capillarity. This phenomenon is called molecular property of matter.

    546. Kepler’s law of planetary motion states that the square of the time period is proportional to the

    (1) semi-major axis
    (2) square of the semi-major axis
    (3) cube of the semi-major axis
    (4) fourth power of the semi-major axis
    Answer:
    546. (3) Kepler’s law of planetary motion states that the square of the time period is proportional to the cube of the semi-major axis.

    547. Radioactive elements can be traced out in living cell through a technique called

    (1) Centrifugation
    (2) Chromatography
    (3) Auto radiography
    (4) All the above
    Answer:
    547. (3) Radioactive elements can be traced out in living cell through a technique called Auto radiography.

    548. A NOT gate can be implemented by:

    (1) a single diode
    (2) two diodes
    (3) a single resistor
    (4) a single transistor
    Answer:
    548. (4) In digital logic, an inverter or NOT gate is a logic gate which implements logical negation. An inverter circuit outputs a voltage representing the opposite logic-level to its input. Inverters can be constructed using a single NMOS transistor or a single PMOS transistor coupled with a resistor.

    549. Persistence of vision is the Principle behind:

    (1) Binocular 
    (2) Cinema
    (3) Periscope 
    (4) Camera
    Answer:
    549. (2) Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina. In the early days of cinema, it was scientifically determined that a frame rate of less than 16 frames per second (frame/s) caused the mind to see flashing images. Audiences still interpret motion at rates as low as ten frames per second or slower, but the flicker caused by the shutter of a film projector is distracting below the 16-frame threshold.

    550. Time of exposure required for taking photograph of an object depends upon the

    (1) brightness of the object
    (2) skill of photographer
    (3) proximity of object
    (4) size of the object
    Answer:
    550. (1) In photography, shutter speed or exposure time is the effective length of time a camera’s shutter is open. The total exposure is proportional to this exposure time, or duration of light reaching the film
    or image sensor. The correct exposure for a particular object depends on the brightness of the object to be photographed.

    551. The ordinary and maximum tolerance limit of sound by human being is

    (1) 50 db to 70 db (decibel)
    (2) 60 db to 80 db (decibel)
    (3) 65 db to 75 db (decibel)
    (4) 70 db to 85 db (decibel)
    Answer:
    551. (2) Normal speech is about 60 dB (decibels). A dangerous sound is anything that is 80 dB or higher which can lead to hearing loss. At 70 dB or lower, the risk of harm to healthy ears is negligible. Listening to sound above 80 decibels can cause profound deafness.

    552. Which one of the following is responsible for the working of Newton’s colour disc experiment ?

    (1) Formation of pure spectra
    (2) Formation of impure spectra
    (3) Persistence of vision
    (4) Principle of complementary colour
    Answer:
    552. (3) A Newton Disc can be created by painting a disc with the seven different colours. A combination of red, green and blue in the circular disc will yield the same result. This is due to the phenomenon called persistence of vision.

    553. The dimension MLT–2 corresponds to

    (1) force 
    (2) work done
    (3) acceleration 
    (4) velocity
    Answer:
    553. (1) The dimensions of Force are M (mass), L (length) and T-2 (time). It can also be expressed as [newton] = [kilogram] [metre] [second]-2.

    554. Fiber optics cable used in communication, works on the principle of

    (1) regular reflection of light
    (2) diffuse reflection of light
    (3) refraction of light
    (4) total internal reflection of light
    Answer:
    554. (4) The use of a long strand of plastic (or other material such as glass) to pipe light from one end of the medium to the other is the basis for modern day use of optical fibers. Since total internal reflection takes place within the fibers, no incident energy is ever lost due to the transmission of light across the boundary.

    555. ‘Farad’ is the unit of :

    (1) Capacitance 
    (2) Inductance
    (3) Resistance 
    (4) Conductance
    Answer:
    555. (1) The Farad is the SI derived unit of capacitance. It is named after the English physicist Michael Faraday.

    556. Steel is more elastic than rubber because it :

    (1) requires larger deforming force
    (2) is never deformed
    (3) is deformed very easily
    (4) is harder than rubber
    Answer:
    556. (3) Elasticity is the capability of an object to return to its former shape once a load inducing strain is removed. Young Modulus or elastic modulus [tendency to be deformed elastically (i.e., non-permanently) when a force is applied to it]of steel is more than that of rubber.

    557. Solids which conduct electricity at higher temperature but not at lower temperature are called

    (1) super-conductor
    (2) metallic-conductor
    (3) semi-conductor
    (4) insulator
    Answer:
    557. (3) Semiconductors are insulators at low temperatures and reasonably good conductors at higher
    temperatures. As temperature increases, the semiconductor material becomes a better and better
    conductor.

    558. A television channel is characterised by

    (1) frequency of transmitted signal
    (2) velocity of transmitted signal
    (3) physical dimension of television screen
    (4) size of picture tube
    Answer:
    558. (1) A television channel is a physical or virtual channel over which a television station or television network is distributed. Channel numbers represent actual frequencies used to broadcast the television signal. For example, in North America, “channel 2” refers to the broadcast or cable band of 54 to 60 MHz, with carrier frequencies of 55.25 MHz for NTSC analog video (VSB) and 59.75 MHz for analog audio (FM), or 55.31 MHz for digital ATSC (8VSB).

    559. The density of water is 1 g/cc. This is strictly valid at

    (1) 0°C 
    (2) 4°C
    (3) 25°C 
    (4) 100°C
    Answer:
    559. (2) Water never has an absolute density because its density varies with temperature. Water has its
    maximum density of 1g/cm3 at 4 degrees Celsius. When the temperature changes from either greater
    or less than 4 degrees, the density will become less than 1 g/cm3. Water has the maximum density of 1
    g/cm3 only when it is pure water.

    560. In radio-communication, the signals emitted by transmitting antenna are reflected on

    (1) stratosphere
    (2) ozonosphere
    (3) ionosphere 
    (4) troposphere
    Answer:
    560. (3) The lower atmosphere is more or less transparent to radio waves. However, the ionosphere reflects back the radio waves. Thus, a signal emitted by an antenna from a certain place can be received at another place on the surface of Earth in the following two ways: ground wave propagation and sky wave propagation.

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