# Physics GK Quiz-5

## Physics GK Quiz-5

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

### 81. Which of the following occurred first ?

(1) Albert Einstein propounded the General Theory of Relativity
(2) Max Planck unveiled the Quantum Theory
(3) Guglielmo Marconi sent out the first wireless signals
(4) Wright Brothers successfully flew an aircraft
81. (3) Guglielmo Marconi sent out the first wireless signals. In the early summer of 1895 and despite an intervening hill, Marconi achieved signal transmission and reception over a distance of about 2km. Success was indicated initially by the waving of a handkerchief and progressed to the need to fire a gun. The theory of relativity transformed theoretical physics and astronomy during the 20th century. When first published, relativity superseded a 200-year-old theory of mechanics stated by Isaac Newton. In 1900 Max Planck made a profound discovery in modern physics / Quantum Theory. He showed (from purely formal / mathematical foundations) that light must be emitted and absorbed in discrete amounts if it was to correctly describe observed phenomena (i.e. Blackbody radiation). The Wright brothers, Orville (August 19, 1871 – January 30, 1948) and Wilbur (April 16, 1867 – May 30, 1912), were two American brothers, inventors, and aviation pioneers who were credited with inventing and building the world’s first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903.

### 82. A passenger standing in a bus is thrown outward when the bus takes a sudden turn. This happens due to

(1) Outward pull on him
(2) Inertia of motion
(3) Change in momentum
(4) Change in acceleration
82. (2) This is inertia of direction. It is the ability of body to be in a state of direction of motion .for example sun holds planets in a fixed elliptical path .this is one of the examples of inertia of direction. Inertia of direction is non-existent however inertia only apply to a body at rest or moving with a constant velocity. It is the property possessed by a body to resist change. In other way we can say that if a body moves in a particular direction under the action of a force and if the force is removed then the will continue to move in the same direction unless stopped under the action of another opposing force for a body at rest it under the inertia of rest whereas inertia of motion is for bodies in motion.

### 83. When pressure is increased the melting point of ice

(1) increases
(2) does not change
(3) decreases
(4) depends on the impurities in the ice
83. (3) In this case, if we increase the pressure on the ice the ice-water system wants to try to lower it again. It can do that by making itself fit into a smaller volume. But since water fills a smaller volume when it’s liquid, rather than solid, it will go to a lower melting point — allowing more solid to become liquid and hence when we increase pressure, the melting point of ice decreases because of the inversal relationship between the pressure and melting point of ice.

### 84. Longitudinal waves cannot travel through

(1) Vacuum
(2) Solid
(3) Liquid
(4) Gas
84. (1 Longitudinal waves cannot travel through vacuum because such wave requires a medium such as solid liquid or air to travel through. They cannot travel through vacuum or in space. Longitudinal waves, also known as “l-waves”, are waves that have the same direction of vibration as their direction of travel, which means that the movement of the medium is in the same direction as, or the opposite direction to, the motion of the wave. Mechanical longitudinal waves are also called compressional waves or compression waves. Longitudinal waves include sound waves (vibrations in pressure, particle displacement, and particle velocity propagated in an elastic medium) and seismic P-waves (created by earthquakes and explosions).

### 85. Electrostatic precipitator is used to control the pollution of

(1) air
(2) water
(3) noise
(4) thermal
85. (1) An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. An electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream. In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).

### 86. Tungsten is used for the manufacture of the filament of an electric bulb, because

(1) It is a good conductor
(2) It is economical
(3) It is malleable
(4) It has a very high melting point
86. (4) Tungsten is used because it has the highest melting point of all the metallic elements. It melts at 3410 degrees Celsius. When current passes through the filament it heats it up. When the filament reaches a certain temperature it starts to give off light, that’s how we get a light bulb. The first successful light bulb filaments were made of carbon (from carbonized paper or bamboo). In 1906, the tungsten filament was introduced. Tungsten metal was initially not available in a form that allowed it to be drawn into fine wires. Filaments made from sintered tungsten powder were quite fragile. The advantage of the coiled coil is that evaporation of the tungsten filament is at the rate of a tungsten cylinder having a diameter equal to that of the coiled coil.

### 87. What is the wavelength of visible spectrum ?

(1) 1300 A°–3000 A°
(2) 3900 A° – 7600 A°
(3) 7800 A° – 8000 A°
(4) 8500 A° – 9800 A°
87. (2) The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be
detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm in terms of angstrom it is in between 3900 A° - 7600 A°. In terms of frequency, this corresponds to a band in the vicinity of 400–790 THz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (luminosity function). The spectrum does not, however, contain all the colours that the human eyes and brain can distinguish. Unsaturated colours such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths.

### 88. Who measured the velocity of light first ?

(1) Galileo
(2) Newton
(3) Romer
(4) Einstein
88. (3) Galileo is often credited with being the first scientist to try to determine the speed of light. Galileo’s experiment was carried out by the Accademia del Cimento of Florence, Italy, in 1667, with the lanterns separated by about one mile, but no delay was observed. The actual delay in this experiment would have been about 11 microseconds. The first quantitative estimate of the speed of light was made in 1676 by Romer. From the observation that the periods of Jupiter’s innermost moon Io appeared to be shorter when the Earth was approaching Jupiter than when receding from it, he concluded that light travels at a finite speed, and estimated that it takes light 22 minutes to cross the diameter of Earth’s orbit.

### 89. When a vehicle passes, TV reception gets distorted. This is because

(2) spark plug creates electromagnetic disturbances
(3) vehicle pollution affects the performance of the TV components
(4) modern vehicles use electroignition system
89. (2) This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.

### 90. The energy emitted by the Sun is due to

(1) Chemical reaction
(2) Nuclear fission
(3) Nuclear fusion
(4) All of the above
90. (3) The spectrum of the Sun’s solar radiation is close to that of a black body with a temperature of about 5,800 K. The Sun emits Electromagnetic radiation across most of the electromagnetic spectrum.
Although the Sun produces Gamma rays as a result of the nuclear fusion process, these super high
energy photons are converted to lower energy photons before they reach the Sun’s surface and are emitted out into space. nuclear fusion is a nuclear reaction in which two or more atomic nuclei join together, or “fuse”, to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released. Fusion is the process that powers active stars. The fusion of two nuclei with lower masses than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy, while the fusion of nuclei heavier than iron absorbs energy.

### 91. The sky appears blue because of

(1) Atmospheric water vapour
(2) Scattering of light
(3) Reflection on sea water
(4) Emision of blue wavelength by the sun
91. (2),The sky is blue because the molecules in the air scatter light in the higher wavelengths (that is, the blue light), while lower wavelength light (that is, the light on the red end of the spectrum) goes through to the ground. So the light that get finally reflected down from the scattering is blue, therefore a blue sky. This is called Rayleigh scattering. Rayleigh scattering, named after the British physicist Lord Rayleigh, is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through transparent solids and liquids, but is most prominently seen in gases.

### 92. Dynamo is a device for converting

(1) Heat energy into electrical energy
(2) Mechanical energy into electrical energy
(3) Magnetic energy into electrical energy
(4) Chemical energy into electrical energy
92. (2) A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry,
and the foundation upon which many other later electric-power conversion devices were based,
including the electric motor, the alternating-current alternator, and the rotary converter. A dynamo has
the disadvantages of a mechanical commutator. Also, converting alternating to direct current using power rectification devices (vacuum tube or more recently solid state) is effective and usually economic.

### 93. Oil rises up the wick in a lamp because

(1) Oil is very light
(2) Of the diffusion of oil through the wick
(3) Of the surface tension phenomenon
(4) Of the capillary action phenomenon
93. (4) It is because of the capillary action phenomenon because of which oil rise up the wick in a lamp.
Capillary action, or capillarity, is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity. The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper, in some non-porous
materials such as liquefied carbon fiber, or in a cell. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces.

### 94. In the atmosphere ultraviolet rays are absorbed by

(1) Oxygen
(2) Nitrogen
(3) Ozone
(4) Helium
94. (1) Most of the ultraviolet radiation in sunlight is absorbed by oxygen in Earth’s atmosphere, which
forms the ozone layer of the lower stratosphere. UV light is found in sunlight (where it constitutes about 10% of the energy in vacuum) and is emitted by electric arcs and specialized lights such as black
lights. It can cause chemical reactions, and causes many substances to glow or fluoresce. Most ultraviolet is classified as non-ionizing radiation. The higher energies of the ultraviolet spectrum from wavelengths about 10 nm to 120 nm (‘extreme’ ultraviolet) are ionizing, but this type of ultraviolet in sunlight is blocked by normal di-oxygen in air, and does not reach the ground. In addition to short wave UV blocked by oxygen, a great deal (>97%) of mid-range ultraviolet (almost all UV above 280 nm and most above 315 nm) is blocked by the ozone layer, and like ionizing short wave UV, would cause much damage to living organisms if it penetrated the atmosphere.

### 95. Which of the following metals is used for the manufacture of heating elements provided in electric iron ?

(1) Nickel
(2) Chromium
(3) Nichrome
(4) Tungsten
95. (3) Nichrome is the most common domestic heating element and is found in many household products. Commonly, items such as toasters, hair dryers and heaters use nichrome coils to pass electricity and give off heat. Nichrome is made of 80 percent nickel and 20 percent chromium, and its high melting point of 1,400 degrees Celsius. Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. Due to its relatively high electrical resistivity and resistance to oxidation at high temperatures, it is widely used in electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters, and even electronic cigarettes.

### 96. An electron microscope gives higher magnification than an optical microscope, because :

(1) it uses more powerful lenses
(2) the velocity of electron is smaller than that of visible light
(3) the electrons have more energy than the light particles
(4) the wavelength of electrons is smaller as compared to the wavelength of visible light
96. (4) 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. Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called “magnification”. When this number is less than one it refers to a reduction in size, sometimes called “de-magnification”.

### 97. The hydraulic brakes used in automobiles is a direct application of :

(1) Archimedes’ principle
(2) Toricellian law
(3) Bernoulli’s theorem
(4) Pascal’s law
97. (4) Pascal’s principle guarantees that the pressure is transmitted equally to all parts of the enclosed fluid system. This gives straight-line braking unless there is a fluid leak or something to cause a significant difference in the friction of the surfaces. 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.

### 98. Where are mesons found ?

(1) Cosmic rays
(2) X-rays
(3) Gamma rays
(4) Laser beam
98. (1) Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks. In cosmic ray interactions,
for example, such particles are ordinary protons and neutrons. Mesons are hadronic subatomic particles
composed of one quark and one anti-quark, bound together by the strong interaction. Because mesons
are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 2/3 the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos.

### 99. Plants are dried up in winter due to frost because

(1) Evaporation does not take place
(2) Photosynthesis does not take place at such low temperature
(3) Respiration does not take place at low temperature
(4) There is mechanical loss of tissues and drought condition prevails
99. (4) Respiration does not rely on the sun, so it is possible for plants to respire around the clock. The
rate of respiration is dependent on temperature: The warmer it is, the more a plant will respire. Drought,
extreme winter or frost and heat injury all create a situation for the plant where moisture is not adequate
to maintain the proper water levels in plant tissues. Extreme winter cold and frost are similar to summer
drought in that frozen water is unavailable to the plant. The air is very dry as well.

### 100. For a body moving with non-uniform velocity and uniform acceleration

(1) Displacement – Time graph is linear
(2) Displacement – Time graph is non-linear
(3) Velocity – Time graph is nonlinear
(4) Velocity – Time graph is linear