Physics GK Quiz-6

Physics GK Quiz-6

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

    101. The fourth state of matter is known as

    (1) Gas 
    (2) Vapour
    (3) Plasma 
    (4) Electrons
    Answer:
    101. (3) The characteristics of plasmas are significantly different from those of ordinary neutral gases so that plasmas are considered a distinct “fourth state of matter. plasma is a state of matter similar to gas in which a certain portion of the particles is ionized. Heating a gas may ionize its molecules or atoms
    (reduce or increase the number of electrons in them), thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions. Ionization can be induced by other means, such as strong electromagnetic field applied with a laser or microwave generator, and is accompanied by the dissociation of molecular bonds, if presents.

    102. Lamberts law is related to

    (1) Reflection
    (2) Refraction
    (3) Interference
    (4) Illumination
    Answer:
    102. (4) Lambert’s Law says that the intensity of emitted light from a surface is directly proportional to the cosine of the angle between the line of view and the normal to the surface. A Lambertian surface is a surface that follows this rule exactly. In practice, most surfaces are not perfectly Lambertian. A surface which obeys Lambert’s law is said to be Lambertian, and exhibits Lambertian reflectance. Such a surface has the same radiance when viewed from any angle. This means, for example, that to the human eye it has the same apparent brightness (or luminance). It has the same radiance because, although the emitted power from a given area element is reduced by the cosine of the emission angle, the apparent size (solid angle) of the observed area, as seen by a viewer, is decreased by a corresponding amount. Therefore, its radiance (power per unit solid angle per unit projected source area) is the same.

    103. Which of the following laws validates the statement that matter can neither be created nor destroyed ?

    (1) Law of conservation of energy
    (2) Le Chatelier’s Principle
    (3) Law of conservation of mass
    (4) Law of osmosis
    Answer:
    103. (3) The law of conservation of mass, also known as the principle of mass/matter conservation, states that the mass of an isolated system (closed to all transfers of matter and energy) will remain constant over time. This principle is equivalent to the conservation of energy: when energy or mass is enclosed in a system and none is allowed in or out, its quantity cannot otherwise change over time (hence, its quantity is “conserved” over time). The mass of an isolated system cannot be changed as a result of processes acting inside the system. The law implies that mass can neither be created nor destroyed, although it may be rearranged in space and changed into different types of particles; and that for any chemical process in an isolated system, the mass of the reactants must equal the mass of the products.

    104. Decibel is the unit used for

    (1) Speed of light
    (2) Intensity of heat
    (3) Intensity of sound
    (4) Radio wave frequency
    Answer:
    104. (3) The decibel (abbreviated dB) is the unit used to measure the intensity of a sound. The decibel scale is a little odd because the human ear is incredibly sensitive. Our ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine. The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. The decibel is used for a wide variety of measurements in science and engineering, most prominently in acoustics, electronics, and control theory.

    105. The term ‘Isoneph’ indicates the lines of equal

    (1) cloudiness 
    (2) salinity
    (3) rainfall 
    (4) pressure
    Answer:
    105. (1) An isoneph is a line indicating equal cloud cover or equal cloudiness. Variations in the degrees of slope, temperature, occurrence of rainfall, may be represented by drawing the lines of equal values on a map. All such maps are termed as Isopleth Map. The word Isopleth is derived from ‘Iso’ meaning equal and ‘pleth’ means lines. Thus, an imaginary line, which joins the places of equal values, is referred as Isopleth. The more frequently drawn isopleths include Isotherm (equal temperature), Isobar (equal pressure), Isohyets (equal rainfall), Isonephs (equal cloudiness), Isohels (equal sunshine), contours (equal heights), Isobaths (equal depths), Isohaline (equal salinity), etc.

    106. The atmospheric layer reflecting radio waves is called

    (1) Ozonosphere
    (2) Ionosphere
    (3) Stratosphere
    (4) Mesosphere
    Answer:
    106. (2) The ionosphere is a part of the upper atmosphere, from about 85 km to 600 km altitude, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the
    magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth, stretching from a height of about 50 km to more than 1000 km. It owes its existence primarily to ultraviolet radiation from the Sun.

    107. ‘Cryogenics’ is a science dealing with

    (1) high temperatures
    (2) low temperatures
    (3) friction and wear
    (4) growth of crystals
    Answer:
    107. (2) Cryogenics is the study of how to get to low temperatures and of how materials behave when they get there. Besides the familiar temperature scales of Fahrenheit and Celsius (Centigrade), cryogenicists use other temperature scales, the Kelvin and Rankine temperature scales. One of the more modern processes being used to treat metals (as well as other materials) is cryogenic tempering. While the science of heat treatment is well known and widely understood, the principles of cryogenic tempering remain a mystery to most people in industry.

    108. The mass-energy relation is the outcome of

    (1) quantum theory
    (2) general theory of relativity
    (3) field theory of energy
    (4) special theory of relativity
    Answer:
    108. (4) Special theory of relativity postulates that the speed of light is a universal constant. We cannot reach speeds greater than the speed of light by the relativistic addition of velocities. The equation is how to reconcile with this result of special relativity with Newton’s second law, F=ma. It would be seen that any constant force, no matter how small, applied for a considerably very long time, should continuously accelerate any mass ‘m’ at a rate a=f/m until the speed was arbitrarily very large. Einstein, concluded that energy has inertia i.e. the more energy a body possess, the more inertia that body will display. Since, inertia is a property of matter, which is associated with mass. Thus from Einstein’s argument mass is simply a property attributed to the total energy of the body and only the total energy is required, to know the total mass of the body.

    109. Which of the following are used for accurately measuring very small time intervals ?

    (1) Pulsars
    (2) Quartz clocks
    (3) Atomic clocks
    (4) White dwarfs
    Answer:
    109. (3) An atomic clock is a clock device that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS.

    110. Why does bleeding occur through the nose in high mountainous regions ?

    (1) The pressure of blood in capillaries is greater than the outside pressure
    (2) The pressure at high altitudes is greater than that on the plains
    (3) The blood pressure of a person increases at high altitudes
    (4) The blood pressure fluctuates and finally decreases drastically
    Answer:
    110. (3) Nose bleeds can occur at high altitudes. The bleeding may be caused by the change in air pressure associated with the change in altitude or the cold dry air common at high altitudes. No matter the cause, the symptoms and treatment of a high altitude bloody nose are the same. A nose bleed is defined as the discharge of blood from the nostrils. Stress and anxiety raises the blood pressure, complicating the nose bleed. At high elevations, there’s less oxygen in the air for us to breathe in. When we travel from a low elevation to a high one, our body needs time to adjust to the lower levels of oxygen reaching your bloodstream. Eventually, our respiration and heart activity increase and we produce more red blood cells to transport the oxygen to where it needs to go.

    111. Danger signals are generally red as red light

    (1) is least bright
    (2) undergoes least deviation
    (3) has lowest velocity
    (4) gives comfort to eye
    Answer:
    111. (2) The primary reason why the colour red is used for danger signals is that red light is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the
    wavelength of a colour. Therefore blue which has the least wavelength of all the visible radiations is
    scattered the most and red which has the highest wavelength of all the colours we can see is scattered
    the least. So red light is able to travel the longest distance through fog, rain, and the alike. Also, red is
    a colour we inherently perceive as one that is associated with danger.

    112. A simple microscope consists of :

    (1) a short focus convex lens
    (2) a long focus convex lens
    (3) a short focus concave lens
    (4) a long focus concave lens
    Answer:
    112. (1) Simple microscope - light microscope consisting of a short focus single convex lens is used to produce an enlarged image. The magnifying glass was invented by Roger Bacon in 1250. In the original ‘simple’ microscopes, a single light path went through the object viewed and one lens, increasing the visibility of the object by some amount (magnification). (One light path, one lens = simple microscope) Compound refers to the fact that in order to enlarge an image; a single light path passes through a series of lenses in a line. Each lens magnifies the image over the previous one. (One light path, multiple lenses = compound microscope) Usually, a modern compound microscope has multiple lenses within the eye tube, and a series of three or four objective lenses on the ‘head’ which can be rotated into place. The image produced is a two dimensional (2-D) image.

    113. An oil drop spreads over water because

    (1) oil is lighter than water
    (2) oil is more viscous
    (3) oil does not mix with water
    (4) surface tension of oil is much smaller than that of water
    Answer:
    113. (4) Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids. Surface tension is responsible for the shape of liquid droplets. Although easily
    deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. Water has the greatest surface tension, due to greater forces between the molecules of water compared to oil (mainly due to hydrogen bonding of water molecules to each other). So an oil droplet spreads over it.

    114. The device which converts AC to DC is

    (1) Oscillator 
    (2) Amplifier
    (3) Rectifier 
    (4) None of these
    Answer:
    114. (3) A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, solid-state diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, detectors of radio signals serve as rectifiers.

    115. Knot is a measure of

    (1) The speed of ship
    (2) The curvature of spherical objects
    (3) Solar radiation
    (4) Intensity of earthquake shock
    Answer:
    115. (1) The knot (pronounced not) is a unit of speed equal to one nautical mile (1.852 km) per hour,
    approximately 1.151 mph. There is no standard abbreviation but km is commonly used. The knot is
    a non-SI unit accepted for use with the International System of Units (SI). Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. The speeds of vessels relative to the fluids in which they travel (boat speeds and air speeds) are measured in knots.

    116. When the main switch of the house is put off it disconnects the

    (1) live wire only
    (2) live wire and the earth wire
    (3) live wire and the neutral wire
    (4) earth wire and the neutral wire
    Answer:
    116. (3) Three wires enter most homes from the power pole—two “hot” wires and a third “neutral” wire. Each hot wire provides 120-volt current for conventional lights, receptacles, and appliances when paired with the neutral wire, which is normally kept at zero volts or “ground potential.” When both hot wires are used together with the neutral, they power large 240-volt appliances such as air conditioners and electric ovens. All the electric appliances stop working in a house when the main switch is put off because the electric circuit (the path where the electricity travels) gets opened. A circuit needs to be closed in order for current to flow through it and thus all electric appliances to work. Switching off the main supply involves breaking the circuit and hence the current flow through the circuit. Turning off a wall switch does not necessarily turn off the power to a fixture or receptacle; the power at the circuit breaker should be shut off. On the electrical box, we can see a row of switch. One main switch is particular unique in colour or size. This is the main switch which cuts off the supply from live and neutral wire. In rest of the switches, only the live wire is disconnected. This is an important note to take, and the same applies to the wall switches.

    117. Heat from the sun reaches earth by the process of

    (1) Conduction
    (2) Convection
    (3) Radiation
    (4) All of the above
    Answer:
    117. (3) In physics, 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. Heat from the sun also reaches earth by the process of radiation.

    118. Boyle’s law is a relationship between

    (1) Pressure and volume
    (2) Volume and temperature
    (3) Volume and density
    (4) Pressure and temperature
    Answer:
    118. (1) Boyle’s law states that the absolute pressure and volume of a given mass of confined gas are inversely proportional, if the temperature remains unchanged within a closed system. Thus, it states that the product of pressure and volume is a constant for a given mass of confined gas as long as the temperature is constant. The law was named after chemist and physicist Robert Boyle, who published the original law in 1662.

    119. Which of the following produces more severe burns ?

    (1) Boiling water
    (2) Hot water
    (3) Steam
    (4) Melting iceberg
    Answer:
    119. (3) A burn is an injury to the body’s tissue resulting from heat, chemicals, electricity or sunlight. Burns are often classified as first degree (those causing damage to the outer layer of the skin, the epidermis), second degree (causing deeper damage to the dermis, the layer beneath the epidermis),third degree (those causing the deepest and most severe damage — destruction of all layers of the skin and damage to tissues underneath. A steam burn is a burn caused by steam, usually from boiling water. Although the skin will not be charred, as would be the case with a flame burn, blisters and redness will appear. A third degree steam burn will penetrate deep into the flesh, and may be white, heavily blistered, and numb. The larger concern with steam burns is the airway, however. Inhaling steam can cause serious damage to the bronchial tubes, and could potentially lead to death.

    120. The sudden fall of atmospheric pressure indicates

    (1) fair weather 
    (2) storm
    (3) rain 
    (4) cold weather
    Answer:
    120. (2) Atmospheric pressure is basically the weight of air in the atmosphere above the reservoir, so the level of mercury continues to change until the weight of mercury in the glass tube is exactly equal to the weight of air above the reservoir. In areas of low pressure, air is rising away from the surface of the
    earth more quickly than it can be replaced by air flowing in from surrounding areas. This reduces the
    weight of air above the reservoir so the mercury level drops to a lower level. A slowly rising atmospheric pressure, over a week or two, typically indicates settled weather that will last a long time. A sudden drop in atmospheric pressure over a few hours often forecasts an approaching storm, with heavy rain and strong winds.

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