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The electrical conductivity of a semiconductor at absolute zero of temperature is zero At room temperature, the conduction band electrons are equal to that of valence band holes in an intrinsic semiconductor If m*h > m*e, then the position of Fermi energy level is just above the center of forbidden energy gap Dual nature [particle and wave] of matter was proposed by de Broglie Spectral line splitting due to the influence of magnetic fields is called Zeeman Effect The Zeeman Effect without the spin of the electron is called Normal Zeeman Effect In semiconductors with the increase in temperature the resistance Decreases Conduction band contains free electrons Semiconductors are material in which conductivity is None of the options A Greater than conductivity of a conductor B less than conductivity of an insulator C Equal to conductivity of a conductor D None of the above Answer D All semiconductors in their last orbit have 4 electrons Hall Effect is associated with Semiconductors What was demonstrated by G. P. Thomson? Diffraction of electrons If line spectrum is subjected to magnetic field, the line splits into a number of components symmetrically distributed about the original line. This effect is known as, Zeeman effect When a beam of monochromatic light passed through organic liquids, the scattered light contained other frequencies in addition to that of the incident light. This effect is known as, Raman Effect Hall effect measurement helps us to get Measurement of magnetic field Sign and Concentration of charge carrier Mobility of charge carriers In Hall Effect if magnetic field is applied along X-axis, current is flowing along Y axis, then in what direction the hall voltage would develop? Perpendicular to magnetic field direction as well as current flow direction Silicon and Germanium element have four valence electrons Valence electrons are the Electrons present in the outermost orbit A Germanium atom contains Four valance electron Free electrons exist in Conduction band The energy band occupied by valence electrons that are incorporated into covalent bonds is called Valence band The energy band hosing the free electrons capable of electrical conduction is called the Conduction band The energy interval between the top edge of valence band and the bottom edge of the conduction band is Forbidden band gap Depending of existence and width of which band the solids are classified as conductors, semiconductors, and insulators? Forbidden band gap At absolute zero temperature, in insulators and semiconductors The valence band is full and conduction band is empty The valence band and conduction band are separated by Forbidden band gap Materials which show negligible conductivity at 0K but exhibit significant Conductivity at normal temperatures are called as, Semiconductors In semiconductor, the forbidden gap Eg typically From 0.5 eV to 1.5 eV In semiconductors, the empty states left behind in the valence band assume particle character and act as charge carriers. These empty states are called as, Holes The uppermost filled energy level in a conductor at 0K -Fermi energy The maximum energy energy that an electron can have in a conductor at 0K -Fermi energy The average energy possessed by the electrons which participate n conduction process in conductors at temperatures above 0K Fermi energy The class of solids in which, at normal temperatures, a significant number of electrons are thermally excited from valence band to conduction band and an equal number of holes are produced in the valance band is............Semiconductors Chemically pure semiconductors are known as Intrinsic semiconductors A semiconductor is considered to be pure when …There is less than one impurity atom in a billion host atoms. Intrinsic semiconductors have Low conductivity An introduction of impurity atoms in an perfect semiconductor gives rise to Extrinsic semiconductors An intentional introduction of controlled quantity of impurity into an intrinsic semiconductor is called as Doping In an intrinsic semiconductor, the concentration of electrons and holes will be equal The process that generates carriers in an intrinsic semiconductors Thermal process The electrical conductivity increases when an intrinsic semiconductor is doped with suitable impurity. Such semiconductor is known as Extrinsic semiconductors Semiconductor doped with pentavalent impurities become 'n' type semiconductor Semiconductor doped with trivalent impurities become 'p' type semiconductor pentavalent impurities are called as Donor impurities trivalent impurities are called as Acceptor impurities In n-type semiconductor, donor levels are near the edge of conduction band. In p-type semiconductor, acceptor levels are near the edge of valance band The more numerous carriers in an extrinsic semiconductor are known as, Majority carriers The less numerous carriers in an extrinsic semiconductor are known as, Minority carriers In case of Raman effect the lines on lower frequency side are more intense and called as, Stokes lines In case of Raman effect the lines on higher frequency side are less intense and called as, Anti - Stokes line Stokes and anti Stoke lines are observed in Raman effect Raman effect can be observed in Benzene Which of the following is magneto-optical phenomenon Zeeman effect The simplest splitting in Zeeman effect is obtained with Strong magnetic field The complex splitting in Zeeman effect is obtained with Weak magnetic field In case of Zeeman effect, longitudinal view reveals Doublet In case of Zeeman effect, transverse view reveals Triplet In Raman effect, in addition to original line New lines symmetric to both sides of mean line are observed In Zeeman effect, splitted spectral line are Circularly polarized The wavelength associated with a particle of mass m moving with velocity v is given by h/mv The product of uncertainties between position and momentum is given by p=h The equation of wavelength of matter wave was derived by de-broglie The wavelength of electron accelerated though the potential V is Inversely proportional to square root of potential V The velocity of matter wave is Larger than the velocity of light The equation of motion of matter wave was derived by Schrodinger The particle is specified by Mass and Velocity The particle is specified by Mass and Momentum The wave is specified by Frequency, Wavelength, Amplitude The time-independent Schrödinger equation is a partial differential equation De-Broglie wavelength of a particle with momentum p is h/p The velocity of matter waves depend upon Velocity of Particle In Fermi-Dirac Distribution function, the probability that the energy level E occupied by Electron Fermi level for extrinsic semiconductor depends on A Donor element B Impurity concentration C Temperature D All of these Answer D When a Pentavalent impurity is added to pure semiconductor it becomes N-Type semiconductor Addition of Pentavalent impurity to a Semiconductor creates Free Electrons A hole in a Semiconductor is defined as a In-complete part of an electron pair bond Fermi energy level for intrinsic semiconductors lies Close to valence band Fermi energy level for p-type extrinsic semiconductors lies Close to conduction band The intrinsic charge concentration Is independent of Fermi level Has an exponential dependence on the band gap value Eg Strongly depends on the temperature The Fermi level in an intrinsic semiconductor may be considered as independent In an n type semiconductor, at T=0K, Fermi level lies midway between the donor levels and the bottom of the conduction band In an p type semiconductor, at T=0K, Fermi level lies midway between the acceptor level and the top of the valence band The Fermi-Dirac distribution function gives fractional occupancy of the energy states Matter waves are present when particles are in motion The wave function of the particle is a solution to the wave equation Schrodinger time in-dependent wave equation is given by 2 +8 2m/h2(E-V) =0 Schrodinger time dependent wave equation is given by H =E Identify the properties of wave function Both Normalize and It must be single valued To prepare a n type semiconductor, the element to be added with tetra valant element is Pentavalent element To prepare a p type semiconductor, the element to be added with tetra valant element is Tri valant element If the Hall coefficient is negative then the semiconductor is n-type The sign of Hall coefficient in p type semiconductor is positive In G. P. Thomson experiment for diffraction, the sample used for diffraction is, Thin film of gold or silver or aluminum Raman effect was discovered while study of scattering of light by liquids Zeeman Effect is a magneto-optic phenomenon which provides a link between spectroscopic and magnetic properties of elements The range of critical length below which Nanomaterials begin to demonstrate new physical or chemical phenomenon is in between 1 to 100 nm The tensile strength of a carbon nano-tube is 100 times that of steel The ratio of thermal conductivity of silver to that of carbon nanotubes is 1: 10 Nano material is an emerging branch of science for designing tools and devices of size: 1 to 100 nm Nanomaterials are a science of creation of: Functional materials Control on the nanometer length scale Exploitation of properties All of the above Nano science involves the manipulation of materials on Atomic Scale, Molecular Scale Micro molecular Scale The change in the properties of Nanomaterials as compared to bulk is because of Both Large surface area to volume ratio and Quantum confinement Materials that are Nano scale in one dimension and are extended in the other two dimensions are Thin film Materials that are Nano scale in two dimensions and are extended in one dimension include Both Nano tubes and Nano wires Materials that are Nano scale in three dimensions are Nano particles The properties of Nanomaterials that differ significantly from the bulk are increased Both Relative surface area and Quantum effect Greater proportion of atoms are found on the surface as the particle decreases in size The quantum effect starts dominating the properties of matter, as the materials particle size reduces to nano scale The Nanomaterials are ________ in nature Hard The Nanomaterials are chemically Active The Nanomaterials are ductile at High temperature In nanometer size range, the hardness increases with Decrease of particle size The density of Nanomaterials is ____________ as compared to its bulk density Lowered Melting temperature of nano Particles gets __________ as compared to bulk melting point Reduced In magnetic properties of Nanomaterials below the critical size, material prefers to be Single domain __________ play an important role in the magnetic properties of nanostructures Surface and interfaces The surface to volume ratio is _______ in Nanomaterials Very large In Nanomaterials ionization potential is ________ when compared with that of the bulk Higher The bulk material when reduced to Nanomaterials will show _____ physical and chemical properties Different Nanomaterials can be synthesized by Top-down approach, Bottom-up approach Gold nono Spheres of 100nm appear Orange Nanomaterials was brought into day light by delivering lectures by Feynman ______ are the extensions of bucky balls Carbon nano tubes As the substance change from bulk to nano range they show the change in the properties like, Opaque material is converted in to transparent Inert material start behaving like catalysts Insulators become conductors The optical properties of nano particles include Opaque substances are converted into transparent material Colors of nano particles depend on the particle size nano particles exhibits photoluminescence but bulk material will not show this effect The change in the properties of Nanomaterials as compared to bulk is because of Large surface area to volume ratio quantum confinement In Nanomaterials with decrease of size the inter-atomic spacing Decreases Nanoparticles are transparent The single domain magnetic particles which do not show coercivity or hysteresis are known as super-paramagnetic particle Which one of the following is a physical process of synthesis of nanoparticles? A sol gel method B Chemical vapor deposition C Mechanical Ball milling D None of these Answer C The method in which small balls are allowed to rotate around a drum and drop on the solid enclosed in drum so that the size of solid is reduced to nano scale is known as, A sol gel method B Chemical vapor deposition C Mechanical Ball milling D None of these Answer C The change in the property of material occurs at nanoscale due to the reason, A High surface to volume ratio B More chemical reactivity C interaction with the environment change D All of these Answer D Which one of the following is not a physical process of synthesis of nanoparticles? A sol gel method B Sputter deposition C Mechanical Ball milling D Physical vapor deposition Answer A Which one of the following is not a chemical process of synthesis of nanoparticles? A sol gel method B collide suspension C inverse micelles D Physical vapor deposition Answer D Which one of the following is a chemical process of synthesis of nanoparticles? A sol gel method B Physical vapor deposition C Mechanical Ball milling D Laser ablation Answer A Mechanical Ball milling is a A top down approach B bottom up approach C top down approach and bottom up approach D None of these Answer A In top down approach of nanoparticles synthesis, A start with large structure and is made nano form B starts with individual atom and made nano structures C starts with nano particles and is made still smaller D None of these Answer A The synthesis method in which, nanoparticles are deposited from the gas phase by heating the material and depositing on a surface under vacuum, is known as, A sol gel method B Chemical vapor deposition C Mechanical Ball milling D Laser ablation Answer B The synthesis method in which, ions are accelerated towards the surface of the target, causing atoms of the source material to break off from the target and condense on the substrate is known as, A sol gel method B Chemical vapor deposition C Mechanical Ball milling D Sputtering Answer D The synthesis method in which, high intensity laser beam is focused on target material, target material converted in to plasma and condense on the substrate at room temperature is known as, A sol gel method B Chemical vapor deposition C Mechanical Ball milling D Laser ablation Answer D Which of the following is not a stage of Sol gel synthesis technique of nanoparticles? A Agglomeration B Condensation C Sputtering D Hydrolysis Answer C Which of the following is a stage of Sol gel synthesis technique of nano particles? A Growth of particles and Agglomeration B Condensation C Hydrolysis D All of these Answer D Synthesis of Nanomaterials, in mechanical ball milling method, size of the containers depends upon the amount of A Grain size B Nature of materials C Type of nanostructure D None of the above Answer A Evaporation can be achieved by A Resistive heating B Laser heating C Both Resistive heating and Laser heating D Mechanical crushing Answer C In evaporation, the number of atoms leaving the surface of solid or liquid material should A Greater than atoms returning to the surface B less than atoms returning to the surface C some times greater than or some times less than atoms returning to the surface D None of these Answer A Sputter deposition can be carried out using A Direct current sputtering B Radio frequency sputtering C Both Direct current sputtering and Radio frequency sputtering D None of the above Answer C In sputter deposition method, discharge of some __________ atoms are used A Inert gas B Iron gas C Carbon di oxide gas D Hydrogen gas Answer A In sputter deposition method, deposition is carried out in a required ___________ obtained in a high vacuum system A Vapor pressure B Atmospheric Pressure C Gas pressure D Both A and B Answer C In chemical method, synthesis of Nanomaterials occur at A Low temperature B High temperature C Stellar temperature D None of these Answer A In chemical method, materials are obtained in the form of ________ but can be converted into dry power or thin films quite easily A solid B liquid C gaseous D plasma Answer B __________ are best synthesized using a Sol-gel method A Argon B Oxide ceramics C Aluminium D Zeolites Answer B The properties of nanoparticles which make them suitable for their use in space technology are, A reduced weight B High tensile strength C low temperature coefficient of expansion D All of these Answer D Cloths made up of nano fabrics are Water and stain repellent Wrinkle free Less frequently washed The environmental applications of nanoparticles include A reduction in pollutants and waste B renewable energy technologies C detects and decomposes toxic gases and hazardous compounds D All the above Answer D In the application of nanoparticles in medical science, drugs can be encapsulated in nano capsules and targeted towards desired part of the body. This technique is known as, A untargeted drug treatment B Site specific drug delivery C random drug treatment D regular drug treatment Answer B Application of nano materials in electronics does not include A Single electron transistor B spintronics C magnetic tunnel junctions D smart clothes Answer D Nanoparticles are used in cosmetic industry as they, A absorb ultraviolet radiation thus protecting skin B appearance of wrinkles suppressed C dyes and colors based on nanoparticles are harmless to the skin D All of these Answer D Nanoparticles are used in textile industry as they, A give pleasant look of synthetic fiber but comfort of cotton B are dirt free and water repellent C protect from germs and bacteria D All of these Answer D Nanomaterials, in other words, is A Bulk engineering B Atomic engineering C Small technology D Microphysics Answer B Nanomaterials are being applied extensively to provide A Drug therapy B Diagnostics C Tissue degeneration D All of the above Answer D There is an increasing use of nanoscale particles in A Stain resistant clothing B Cosmetics C Sunscreens D All of these Answer D Scientists, researchers and medical personnel can ensure to do: A Small things using the very big B Big things using the very small C Both of the above D None of the above Answer B Nano scale magnetic materials are applied in, A Data storage B Cosmetics C Construction D None of these Answer A The application of Nanomaterials in the automobile industry does not include A friction free spares B Paining and sensors C Long life tires with fillers D Smart cloths Answer D Which device is not based on Nanomaterials? A Single electron transistor B Spin valves C Transformer D Magnetic tunnel junction Answer C Spin valve type devices are used in personal computer to read disk which have enabled to A increase data storage capacity of hard disk B decrease data storage capacity of hard disk C both A and B D None of these Answer A Very low density materials, known as A Sol B Gel C Aerogel D Both A and B Answer C Some special lightweight suits, jackets can be made using A aerogels B Sol C Gel D Iron Answer A Aerogel Material is 10 times lighter than iron Nanocomposite of Fe2O3 and Aluminium burns much faster and is more sensitive than conventional thermites Germ free clothes can be obtained using __________ nanoparticles Silver __________ Nanoparticles of uniform size are able to absorb ultraviolet light and protect the skin A zinc oxide and titanium oxide B zinc chloride and titanium oxide C titanium chloride and zinc chloride D zinc oxide and titanium chloride Answer A Cloths made up of nano fabrics are A Water and stain repellent B Wrinkle free C Less frequently washed D All the above Answer D Which one of the following synthesis methods is superior for production of nano materials in view of purity? A sol gel B mechanical ball milling C sputter deposition D physical vapor deposition Answer A Which one of the following synthesis methods produces large quantity of nano materials at low cost? A sol gel B mechanical ball milling C sputter deposition D physical vapor deposition What characteristic of sol gel technique makes it superior? Large quantity production Highly pure product Production at low cost Carbon nano tube is a cylindrical rolled up sheet of Graphene CNT is a short form of Carbon nano tubes Single domain nanoparticles do not show hysteresis For increasing the performance of solar panels, which of the following nano materials are used, Thin films quantum dots Nano tubes Separation of carbon di oxide gas from automobile and industrial emission to reduce the green house effect is an application of Nanomaterials in the, Environmental science Which of the following is not the characteristic of a LASER source Divergence What is the full form of LASER Light amplification by stimulated emission of radiation Which of the following are the characteristics shown by laser beam A Coherence B High intensity C monochromatic D All of these As compared Laser, ordinary light does not have A monochromaticity B coherence C Large intensity Answer All of these Taking atoms from excited state to ground state by photon hitting the excited atom is known as, stimulated emission Atoms in the ground state absorb the energy photon and rose to excited state. This interaction is known as, Absorption of radiation The natural tendency of atoms in the excited state to release the photon and return to the ground state is known as, spontaneous emission Population Inversion means, More number of atoms in the excited state The method of raising the particles from lower energy state to higher energy state so that population inversion achieved is called, Pumping mechanism An energy state which has longer life time as compared to excited state is known as Metastable state An energy state which have highest life time and in which atoms are most stable is, Ground state Population inversion is completed in certain medium so that laser beam can be produced. Such a medium is known as, Active medium The emission responsible for producing laser is, Stimulated emission Population inversion in preparing a laser beam can be achieved when one of the excited states is more populated than the ground state Stimulated emission process is favored whenever Population inversion is attained In a three level pumping mechanism, which one of the following energy state is not present? non radiative transition state In a three level pumping mechanism, how many energy states are present? three In a four level pumping mechanism, how many energy states are present? four The laser action takes place when a transition of atoms occurs from Metastable state to any lower energy state In ruby laser which part acts as an active medium material Ruby rod Ruby laser is a Solid state laser Ruby laser is a_ Three level laser system In Ruby laser optical pumping is achieved by _ Xenon Flash lamp Ruby laser is a pulsed laser source Ruby rod is made up of Aluminum oxide Al2O3 + Chromium Oxide Cr2O3 In ruby laser, population inversion is achieved by Optical pumping The wavelength of the emitted light in Ruby laser is 6943 Å He-Ne Laser is a Gaseous laser He-Ne laser is a _ Continuous laser He-Ne Laser is a Four level laser system In He-Ne laser system, the helium and neon gases respectively maintained at a ratio 10:1 In He-Ne laser, neon atoms obtain energy On collision from Helium atoms In He-Ne laser, population inversion is achieved by Electrical pumping The active medium for a He-Ne laser is mixture of He and Ne atoms The wavelength of the emitted light in He-Ne laser is 6328 Å Which of the following is a gas laser? He-Ne laser Which of the following is a solid state laser? Ruby laser In a semiconductor laser, the active medium is heavily doped p and n region In a semiconductor laser, the p-n junction is connected in forward bias In a semiconductor laser, the population inversion is achieved in depletion layer Semiconductor laser can be achieved in Ga-As The structure of optical fiber from centre to outside is, Core, cladding and Protecting Sheath An optical fiber is based on the principal of total internal reflection The sheath of an optical fiber enables A to prevent from mechanical abrasions B to prevent interaction with other signals C to prevent from moisture trapping all of these In case of optical fiber, the innermost region through which the signal light is guided is known as, Core In case of optical fiber, the core is surrounded by a coaxial middle region known as, Cladding In case of optical fiber, the outermost region known as, Protecting Sheath For optical fiber to transmit the signal, the necessary condition is given by refractive index of core should be greater than refractive index of cladding In a graded index fiber, the refractive index Decreases parabolically along the radius of the core In step index fiber, the refractive index Changes abruptly at the core cladding interface A number which defines the light gathering capacity of an optical fiber is known as numerical aperture In case of optical fiber, the number which is defined as the sin of the acceptance angle is called as, numerical aperture The angle of incidence made by the ray with the axis of the optical fiber such that it strikes at critical angle at core cladding interface is known as the -Acceptance angle A maximum angle that a light signal can have relative to the axis of the fiber, get transmitted in the fiber and propagate down the fiber is known as, Acceptance angle The correct expression for the acceptance angle is, where n1 and n2 are refractive indices of core and cladding, The light signal incident at acceptance angle gets completely transmitted in the fiber ( ) All the beams entering the fiber within the acceptance angle travel along the length of fiber. The cone formed by the range of angles within acceptance angle is called as , Acceptance cone The light rays contained within the core having the full angle 2 are accepted and transmitted along the fiber. This cone is called as, Acceptance cone If n1 is refractive index of core and n2 is refractive index of cladding, then the expression for numerical aperture of the optical fiber is, ) Answer ( Which one of the following is not a class of optical fiber, Single mode graded index fiber Which of the following is the application of optical fiber? A In communication applications B In military applications, by replacing heavy wires with light weight cables C In temperature and pressure sensors as couplers D All of these Answer D All of these What is nature of output of 0.05% Cr2O3 doped ruby laser? pulsed Acceptance angle is the Maximum angle of incidence Probability of spontaneous emission increases rapidly with increase of Energy difference between two states Resonant cavity in semiconductor-lasers consists of Intrinsic region Pumping source preferred for gaseous lasers is Electrical Pumping The time during which a particle can remain in the excited state is Life time In the process of excitation, the energy is absorbed In the process of de-excitation, photon is emitted Spontaneous emission is incoherent In stimulated emission the incident photon and emitted photon are Coherent with each other In inverted population always the population of higher energy state is a) More than lower energy state Ruby is a crystal of Al2O3 In Ruby crystal aluminum atoms are replaced by Cr2O3 Ruby crystal contains the Chromium about 0.05% Colour of Chromium is Pink Dimensions of the Ruby rod are 4 cm length, 0.5 cm in diameter 28) The Ruby rod is surrounded by a helical Xenon flash tube 31) Population inversion occurs in non-equilibrium state 34) Transmission loss of optical fiber compared to copper wire is lower 36) Step index fiber sustains only Single mode of propagation Multimode of propagation 37) Compared to copper cable the information carrying capacity of optical fiber system is Superior 43) In optical fiber, ray undergoes total internal reflection only if angle of incidence is greater than critical angle 46) In fiber optics, the signal source is Light waves. 52) The main drawback of ruby laser is that the output beam is not continuous 53) The main advantages of gas lasers are Monochromatic, pure spectrum 55) The gas laser consist of a fused Quartz tube 58) Mixture of He : Ne is filled in the tube with pressure of 1.0: 0.1 mm of Hg 59) In Gas laser tube is filled with majority of He and minority of Ne 60) In Gas laser, excited He atoms colloid with Ne atoms 61) Excited state has life time 10-8 sec 63) 10-3 sec is the life time of metastable state 64) Semiconductor diode laser have sides of the order of 1mm 65) In semiconductor diode laser thickness of the active region is 1µm 66) To achieve population inversion in a semiconductor diode, pn junction should be heavily doped 67) Laser is a device which gives output in the form of an intense, coherent and monochromatic beam of light 71) In a p-n junction diode laser, the role of pumping agent is played by forward current 73) An optical fiber has a shape of cylindrical 75) An optical fiber consists of an inner cylinder called the core 76) In optical fiber, light carried by Core 82) Numerical aperture of fiber is a measure of light Gathering power The problem of satisfactory speech at the music in a hall is tackled by the scientist Sabine Acoustics is the science which deals with planning of a building to provide best Audible sound Branch of engineering which deals with better audibility of sound is called as… Architectural acoustics In case of good acoustics the reverberation time for music be 1 to 2 sec In case of good acoustics the reverberation time for speech should be 0.5 to 1 sec Persistence of sound after the source has stopped to emit the sound is called as Reverberation The coefficient of absorption of a material is defined as the ratio of the sound energy absorbed by the surface to that of the total incident sound energy on the surface The absorption coefficient is measured in O.W.U. The reverberation can be controlled by having full capacity of audience and the walls are lined with absorbent materials The materials used to reduce the reflection of sound waves in a room are known as, sound Absorbing materials The walls of a hall built for music concerns should absorb sound An echo is heard when direct and reflected sound waves reach the listener with a time interval of about 1/7 sec Relation between intensity of original sound (IO) & the intensity of sound after reverberation (It) is It/IO=10-6 The sound waves having frequency greater than 20 KHZ are known as Ultrasonic Waves Compared to audible sound, wavelength of ultrasonic waves is small Magnetostriction method is used when frequencies needed are 100 KHZ In Magnetostriction method, rod used is made up of Ferromagnetic material In Magnetostriction method, the field applied on the ferromagnetic rod is, magnetic field In Piezo electric method, the field applied on the crystal is, Electric field In Magnetostriction method, resonance occurs when frequency of the alternating current and the natural frequency of the rod are equal The ferromagnetic rod sends out ultrasonic waves, if the applied frequency and ultrasonic frequency are in the same order In Magnetostriction method, a short nickel rod is clamped at the Center In Magnetostriction method, resonant vibrations occur when the natural frequency of the rod is same as the frequency of the Plate circuit In Piezoelectric method, vibrations are produced when the natural frequency of the crystal coincides with the frequency of the Electric oscillations Ultrasonic waves are produced when the quartz crystal is set into mechanical Vibrations By using Piezoelectric method ultrasonic waves are obtained up to a frequency of 500 KHZ Sound waves having frequency less than 20 Hz are called as Infrasonic The speed of propagation of ultrasonic waves increases with increase in Frequency Ultrasonic waves are the waves having Small wavelength, greater frequency By using ultrasonic waves, depth of the sea is equal to Vt/2 The coefficient of absorption of an open window is taken as 1 The time for which the sound persists in the hall is called as Reverberation Time Reverberation Time is measured in B Open Window unit (OWU) The unit of absorption coefficient is Seconds What will be the reverberation time of the hall if the volume of the hall is 1200 meter cube and total absorption in hall is 110 metric Sabine? 1.8 S A hall has a volume of 7500 meter cube. It is required to have reverberation time of 1.5 seconds. What should be the total absorption in the hall? 825 OWU The correct expression for Sabine’s formula is = Reverberation time T can be expressed as The Reverberation time T depends upon, A the reflecting properties of the walls, floor and ceiling B volume of the hall C coefficient of absorption D All of these Answer D All of these The factors which determine the acoustical quality of the hall are, A The initial sound from the source should be of adequate intensity B The sound should be evenly spread over the whole area covered by the audience C The successive sounds should be clear and distinct. D All of these Answer D All of these The factors that are to be considered in acoustical design of the hall are, A Site selection B Volume, shape and seating arrangement of the hall C Proper reverberation and reverberation time D All of these Answer D All of these The classes of acoustical materials are, A Porous and composite material B Resonant panels C Cavity resonator D All of these Answer D All of these The class of acoustical material which is effective in the higher frequencies are Porous material The class of acoustical material which is effective at lower frequencies are Resonant panels The class of acoustical material which can be designed to absorb any specific frequency is called as Cavity resonator The class of acoustical material which combines the functions of all type of acoustical materials is known as, Composite absorbers The absorption coefficient is defined as, A = The sound heard due to reflection from an obstacle is known as Echo The persistence of audible sound after the source has stopped to emit the sound is known as Reverberation The time taken by sound to fall to one millionth of its intensity and become inaudible, when the source stopped sounding is known as Reverberation time The frequency of ultrasonics is above 20,000 Hz Ultrasonic waves can be heard by bat Ultrasonic waves are Longitudinal Ultrasonic waves are Mechanical vibrations Bats detect obstacles in their path by producing pulses of ultrasonic waves Ultrasonic waves can be used to determine the depth of sea by echo-sounding because of their A Large velocity B Small velocity C Small wavelength D Large wavelength Answer C Small wavelength Out of the following, which is not a property exhibited by ultrasonic waves, A The wavelength of ultrasonic waves is very small B They produces cavitation effect in liquids C ultrasonic waves has a great penetration power D They are less energetic Answer D they are less energetic The full form of SONAR application of ultrasonic waves is, Sound navigation and ranging The applications of ultrasonic waves are A Echo sounder and SONAR B Non destructive testing C Welding, soldering and Cleaning D All of these Answer D All of these When an ac voltage is applied across a quartz crystal, it vibrates at the frequency of the applied voltage. This effect is known as, Piezoelectric effect When a rod of ferromagnetic material, is kept in a magnetic field parallel to its length, the rod suffers a change in its length. This phenomenon is known as, Magnetostriction effect The range of sound wave frequencies which human ear can hear is known as, audible range