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PHY119 Viva MCQs Instructions: 1. It has more than 200 questions and study accordingly required and solved relevant questions. 2. Notes are already shared in all the official and telegram groups. 3. Subscribe to our community by joining our official community given at the end of notes for more such notes and live lectures. UNIT:1 Crystal Structure and X-ray Diffraction X-ray crystallography uses which characteristic of light? a) Polarization b) Interference c) Diffraction d) Coherency View Answer Answer: c Explanation: X-ray crystallography is used to identify the molecular and atomic structure of the crystal. The crystal diffracts the incident X-ray beam. By measuring the intensities and angle of these diffracted beams, the molecular structure of the crystal can be evaluated. 2. X-ray crystallography uses which law for its implementation? a) Einstein’s law b) Planck’s law c) Bragg’s law d) Compton law View Answer Answer: c Explanation: Bragg’s law is used for the identification of the crystal structure of the lattice. X-ray crystallography used it to identify molecular and/or

atomic structure. 3. Which mathematical method is used in X-ray crystallography? a) Fourier Transform b) Partial differentiation c) Geiger method d) Permutation View Answer Answer: a Explanation: In X-ray crystallography, the two-dimensional image formed is converted into three-dimensional form using the mathematical concept of Fourier transformation. 4. X-rays scattering in X-ray crystallographic is elastic. a) True b) False View Answer Answer: a Explanation: For all the X-ray diffraction methods used in X-ray crystallography, the scattered X-ray is elastic; the scattered X-ray have the same wavelength as incident X-ray. 5. Which method is used for identifying the crystal structure of Nanocrystalline powders? a) X-ray crystallography b) Electron crystallography c) Gamma-ray crystallography d) Cannot be identified View Answer Answer: b Explanation: For Nano-crystalline powders, electron crystallography is used for identifying the atomic structure. X-ray crystallography cannot be used in this case. 6. The synchrotron radiation emitted is Polarized.

a) True b) False View Answer Answer: a Explanation: When electrons are accelerated using a synchrotron, radiation called synchrotron radiation is emitted. This radiation is polarized as the electric and magnetic fields of the photons all lie in the same direction. 7. In single X-ray diffraction measurement, the crystal is mounted on __________ a) X-ray source b) Goniometer c) Diffraction Plate d) Fluorescent plate View Answer Answer: b Explanation: It is only by the diffraction of light when passing through the crystal that the structure of a crystal is identified. The goniometer is a device that is used to position the crystal at selected orientations. In a single-crystal X-ray diffraction measurement, the crystal is mounted on it. 8. Inelastic X-rays scattering method are used for the study of __________ a) Photons b) Atoms c) Molecules d) Phonons View Answer Answer: d Explanation: Inelastic X-rays scattering method are useful in studying the excitation of samples such a Plasmon, phonon, Magnons, etc. Phonons are quanta of sound waves. 9. XRD stands for _________ a) X-ray diffraction b) X-rays dispersion c) X-ray powder diffraction

d) X-ray powder dispersion View Answer Answer: c Explanation: XRD stands for X-ray powder diffraction. Phase identification of crystalline material can be done using XRD and it can provide information on unit cell dimensions. This technique is utilized in X-ray crystallography. 10. Identify the process.

a) X-ray scan b) C.T. scan c) X-ray crystallography d) X-ray production View Answer Answer: c Explanation: X-ray crystallography is used to identify the molecular and atomic structure of the crystal. The crystal diffracts the incident X-ray beam. By measuring the intensities and angle of these diffracted beams, the molecular structure of the crystal can be evaluated.

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Properties of X-Rays”. 1. X-rays are weightless. a) True b) False View Answer Answer: a Explanation: X-rays are considered to be pure energy, no mass. They transfer energy from one point to another in the form of quanta/photon. 2. In free space, X-ray travels in ______________

a) Periodic oscillations b) Non-Periodic oscillations c) Zig-zag path d) Straight line View Answer Answer: d Explanation: In free space, X-ray travels in a straight line. The X-ray moves with the speed of light (3 X 108 m/s) and is an electromagnetic wave. 3. X-Rays can be focused on to single point. a) True b) False View Answer Answer: b Explanation: X-rays cannot be focused onto a single point. They interact weakly with matter and the x-ray refractive index for most of the materials is very close to 1.0. 4. Fluorescence is the property when X-ray falls on a material it emits __________ a) Infrared Waves b) Visible Light c) Gamma rays d) UV light View Answer Answer: b Explanation: When X-ray is incident on a specific material, it emits visible light. It happens because it excites the electron to a higher state which when jumps back to a lower state, releases photons. This property of X-ray is known as Fluorescence. 5. X-ray lies in which region of the electromagnetic spectrum? a) 10 Å to 7000 Å b) 4000 Å to 10 Å c) 10 Å to 0.01 Å d) 1 Å to 10 Å

View Answer Answer: c Explanation: X-ray is an electromagnetic wave. It cannot be seen, smelt or heard. Its wavelength range is from 10 Å to 0.01 Å. Beyond X-rays lies Gamma rays. 6. The accelerating potential for an X-ray is 40 kV. What should be the minimum wavelength of the X-ray? a) 0.024 nm b) 0.031 nm c) 0.097 nm d) 0.054 nm View Answer Answer: b Explanation: We know, λmin = 1.24 X 10-6 Vm/ V Here, V = 40 kV= 40000 V Therefore, λmin = 1.24 X 10-6 Vm/ 40000 V = 0.031 nm. 7. What is the effect of X-ray on methylene blue? a) The crystal structure changes b) It’s boiling point increases c) It’s boiling point decreases d) It gets bleached View Answer Answer: d Explanation: X-ray induces color change of many substances. When it is incident on Methyl orange, it causes methyl orange to get bleached. This is the chemical property of X-ray. 8. Which radical is generated in water by X-ray? a) H2°

b) O2° c) OH° d) O° View Answer Answer: c Explanation: X-ray can be used to bring about a chemical change in a reaction as it can produce the highly active OH radical in water. 9. The following X-ray spectrum is for which material?

a) Tungsten b) Molybdenum c) Sodium d) Uranium View Answer Answer: b Explanation: The following X-ray spectrum is for Molybdenum at 35 kV accelerating potential. Thus we can see that at a specific wavelength, a peak in the graph is observed.

10. The following figure shows a __________

a) X-ray scanner b) X-ray tube c) X-ray crystallographer d) X-ray diffraction View Answer Answer: b Explanation: The given figure shows an X-ray tube. In this tube, X-rays are created by the collision of accelerating electron with a metal.

Unit-2: Dielectric and Magnetic Properties of Materials 1. The forbidden energy gap of dielectrics is __________ a) Less than 1.2 eV b) Greater than or equal to 1.2 eV c) Less than 3 eV d) Greater than or equal to 3 eV View Answer Answer: d Explanation: Dielectrics are the materials devoid of free charges. An ideal dielectric is one which is completely devoid of charges. They have a forbidden energy gap of >=3eV. 2. Dipoles are created when dielectric is placed in __________

a) Magnetic Field b) Electric field c) Vacuum d) Inert Environment View Answer Answer: b Explanation: When the dielectric is placed in an electric field, like between the parallel plates of a capacitor, the dipoles are created and they tend to align themselves parallel to the direction of the field. 3. CO2 is a polar dielectric. a) True b) False View Answer Answer: b Explanation: In CO2, the atoms are aligned in a symmetric way. Thus, the centers of positive and negative charge coincide and the molecule has no net charge and a zero dipole moment. Hence, it is a non-polar dielectric. 4. The torque induced on a dipole when placed in an electric field E is given by _________ a) Esinθ b) pEsinθ c) Ecosθ d) pEcosθ View Answer Answer: b Explanation: The torque on the dipole when it is placed in an electric field is given by: pEsinθ. It tends to align the dipole in the direction of the electric field. 5. The dipole is most stable when the angle between the dipole and the field is __________ a) 0° b) 45° c) 90°

d) 180° View Answer Answer: a Explanation: The potential energy of a dipole is given by -pEcosθ. Thus the dipole would be most stable when potential energy would be minimum. Hence, when θ = 0, i.e., the dipole is aligned in the direction of the field, the dipole would be most stable. 6. What is the value of 1 Debye in cm? a) 3.33 X 10-28 cm b) 3.33 X 10-30 cm c) 3.33 X 10-32 cm d) 3.33 X 10-34 cm View Answer Answer: b Explanation: Debye is the unit in which the dipole moment of a dipole is calculated. The value of 1 Debye is equal to 3.33 X 10-30 cm or 3.33 X 1032 m. 7. Polarization is defined as the dipole moment __________ a) per unit length b) per unit area c) per unit volume d) per unit time View Answer Answer: c Explanation: When a dipole is placed in an electric field, the positive charges appear near the negative electrode and negative charges near the positive electrode. This phenomenon is called polarization which is defined as Dipole moment per unit volume. 8. In a water drop of radius 1 mm all the molecular dipole points are in the same direction. If the dipole moment of a water molecule is 6 X 10-30 m, the polarization in the water drop is ___________ a) 6.4 X 10-13 m-2 b) 7.4 X 10-13 m-2

c) 8.4 X 10-13 m-2 d) 9.4 X 10-13 m-2 View Answer Answer: c Explanation: Molecular mass of water = 18 gm 18 gm of water contains 6.023 X 1023 molecules 18/103 m3 of water contains 6.023 X 1026/18 molecules Volume of water drop = 4π/3 X (10-3)3 m3 No of molecules in the drop, N = 6.023 X 1026 X 4π X 10-9/18 X 3 = 1.4 X 1017 m-3 Polarization, P = Np = 1.4 X 1017 m-3 X 6 X 10-30 m = 8.4 X 10-13 m-2. 9. What is the direction of electric field?

a) Right to Left

b) Up to Down c) Down to Up d) Left to Right View Answer Answer: d Explanation: As seen in the figure, the dipoles are arranged in such a way that the positive charge is on the right and negative charge on the left. Thus, the electric field is from left to right. 10. In the formula, P = χeE, what is χe called? a) Electric constant b) Polarizing constant c) Electric susceptibility d) Polarizing susceptibility View Answer Answer: c Explanation: In the given expression, χe is a constant characteristic of the dielectric and is known as the electric susceptibility of the dielectric medium. 11. H2O is a polar dielectric. a) True b) False View Answer Answer: a Explanation: In H2O, the atoms are aligned in a symmetric way. However, as the electronegativity of oxygen is higher than hydrogen, it pulls the electronic cloud towards itself and it results in a net dipole moment. 12. What is the new capacitance of the plates, when a slab of Dielectric Constant K and thickness one-fourth of the separation of plate is inserted between the plates? a) 4KCo/K + 2 b) 4KCo/1 + 2K c) 4KCo/K + 3 d) 4KCo/1 + 3K View Answer

Answer: d Explanation: As the slab is inserted between the plates, V = E0(d/4)/K + Eo(3d/4) = Eod (1/4K + 3/4) = Vo(1+3K)/4K Now we know, C = Qo/V = 4KCo/(1 + 3K). 13. The expression for electric susceptibility is ___________ a) εoE b) εoEK c) εoE (K + 1) d) εoE (K – 1) View Answer Answer: c Explanation: Electric susceptibility of a dielectric medium is a constant characteristic of the dielectric. The electric susceptibility is given by εoE (K – 1). 14. The relative dielectric constant of polystyrene is 2.5. What is the polarization produced when 0.5 mm thick sheet of polystyrene is subjected to 220 V? a) 2.78 X 10-6 C/m b) 3.91 X 10-6 C/m c) 4.12 X 10-6 C/m d) 5.84 X 10-6 C/m View Answer Answer: d Explanation: We know, Polarization, P = εo(εr – 1)E

Here, εr = 2.5 E = V/d = 220 / 0.5 X 10-3 = 4.4 X 105 Vm εo = 8.85 X 10-12 C/Vm Hence, P = 8.85 X 10-12 X (2.5 – 1) X 4.4 X 105 C/m2 = 5.84 X 10-6 C/m. 1. The four types of polarization are Electronic Polarization, Ionic Polarization, Space-charge polarization and ______ a) Magnetic Polarization b) Electric Polarization c) Orientational Polarization d) Potential Polarization View Answer Answer: c Explanation: The total polarization in a specimen may comprise of the following four components: Electronic polarization, orientational polarization, ionic polarization and space charge polarization. 2. NaCl falls under which category of polarization? a) Ionic Polarization b) Space-charge polarization c) Dipolar Polarization d) Electronic Polarization View Answer Answer: a Explanation: NaCl contains ionic bond, due to which it has a longer bong length. It is polarized due to the displacement of ions and hence is called,

ionic polarization. 3. Electronic polarizability is dependent of temperature. a) True b) False View Answer Answer: b Explanation: When there is a displacement in the center of electrons and nuclei due to the presence of an electric field, it is called as electronic polarization. The ration of the induced dipole to the field is called electronic polarizability which is independent of temperature. 4. In which category of polarization Electric field is used to develop a net dipole moment in dipolar substances? a) Ionic Polarization b) Space-charge polarization c) Orientational Polarization d) Electronic Polarization View Answer Answer: c Explanation: Dipolar substance possess a permanent dipole moment. However, in the absence of an electric field, they are aligned in a way that they cancel out the net dipole moment. Thus, the orientational polarization is due to the fact that it is because of the orientation of pre-existing dipoles. 5. The dipole is least stable when the angle between the dipole and the field is _____________ a) 0° b) 45° c) 90° d) 180° View Answer Answer: d Explanation: The potential energy of a dipole is given by: -pEcosθ. Thus the dipole would be least stable when potential energy would be maximum. Hence, when θ = 180°, i.e., the dipole is aligned opposite the direction of the

field, the dipole would be least stable. 6. Space charge polarization is mostly observed in ____________ a) Uni-phasic material b) Biphasic material c) Multiphasic material d) Crystal View Answer Answer: c Explanation: In multiphasic material, the charges accumulate at the interface of the phases and at the electrodes. The ions diffuse over appreciable distances giving rise to space-charge polarization. 7. Which category of polarizability strongly depends on Temperature and frequency? a) Ionic Polarization b) Space-charge polarization c) Orientational Polarization d) Electronic Polarization View Answer Answer: c Explanation: Orientational Polarizability exhibits strong dependence on both frequency and temperature while the electronic and ionic components are nearly independent of temperature and frequency. 8. The frequency for electronic polarization lies in which region of the electromagnetic spectrum? a) Microwave b) Infrared c) Visible d) Ultraviolet View Answer Answer: d Explanation: The frequency for electronic polarization lies in the ultraviolet region. For the space-charge it lies in machine frequency, for the dipolar polarization it lies in the microwave region and for the ionic it lies in the

infrared region. 9. Which polarizability is the ionic polarizability?

a) αa b) αb c) αc d) αd View Answer Answer: c Explanation: The following graph shows the variation of total polarizability with the frequency. In the graph. αa is for the space-charge polarizability, αb is for the orientational polarizability, αc is the ionic polarizability and αd is the electronic polarizability. 10. What is the polarizability of an argon atom if the relative permittivity of argon at NTP is 1.000435? a) 1.21 X 10-40 Fm2 b) 1.37 X 10-40 Fm2 c) 1.43 X 10-40 Fm2 d) 1.55 X 10-40 Fm2 View Answer Answer: c Explanation: Number of argon atoms at NTP = 6.023 X 1026/22.4

= 2.69 X 1025 We know, εo(εr – 1) = Nαe αe = εo(εr – 1)/N = 8.85 X 10-12 X 0.000435/ 2.69 X 1025 = 1.43 X 10-40 Fm2. 11. An oxygen atom produced a dipole moment of 5 X 10-23 cm when subjected to an electric field. If the separation between the center of electronic cloud and the nucleus is 4 X 10-17 m, what is the polarizability of the oxygen atom? a) 1.4 X 10-47 Fm2 b) 1.7 X 10-47 Fm2 c) 1.8 X 10-47 Fm2 d) 1.9 X 10-47 Fm2 View Answer Answer: d Explanation: If d is the separation between the centers, then E = 8ⅇ/(4πε0 d) = 8 X 1.6 X 10-19/4 X 3.14 X 8.85 X 10-12 X 16 X 10-34 = 2.6 X 1024 V/m Also, p = αE Therefore, α = p/E = 1.9 X 10-47 Fm2. 12. The dielectric constant of helium is 1.000684. If N is 2.7 X 1025 atoms/m3, what is the radius of the electronic cloud?

a) 3.78 X 10-11 m b) 4.65 X 10-11 m c) 5.87 X 10-11 m d) 6.12 X 10-11 m View Answer Answer: c Explanation: We know, εo(εr – 1) = Nαe Or, N4πεor3 = εo(εr – 1) r3 = (εr – 1)/N4π Here, (εr – 1) = 0.000684, N = 2.7 X 1025 atoms/m3, we get r3 = 0.000684/4 X 3.14 X 2.7 X 1025 r = 5.87 X 10-11 m. 13. In a water drop of radius 1 mm all the molecular dipole points are in the same direction. If the dipole moment of a water molecule is 6 X 10-30 m, the polarization in the water drop is _____________ a) 6.4 X 10-13 m-2 b) 7.4 X 10-13 m-2 c) 8.4 X 10-13 m-2 d) 9.4 X 10-13 m-2 View Answer 14. The relative dielectric constant of polystyrene is 2.5. What is the polarization produced when 0.5 mm thick sheet of polystyrene is subjected to 220 V? a) 2.78 X 10-6 C/m b) 3.91 X 10-6 C/m c) 4.12 X 10-6 C/m d) 5.84 X 10-6 C/m View Answer Answer: d Explanation: We know, Polarization, P = εo(εr – 1)E

Here, εr = 2.5 E = V/d = 220 / 0.5 X 10-3 = 4.4 X 105 Vm εo = 8.85 X 10-12 C/Vm Hence, P = 8.85 X 10-12 X (2.5 – 1) X 4.4 X 105 C/m2 = 5.84 X 10-6 C/m. 15. What does the following figure shows?

a) Ionic Polarization b) Space-charge polarization c) Orientational Polarization d) Electronic Polarization View Answer Answer: a Explanation: The following figure shows ionic polarization in an ionic crystal. The specimen gets polarized due to the displacement of the ions.

1. The presence of parallel alignment of magnetic dipole moment is given by which materials? a) Diamagnetic b) Ferromagnetic c) Paramagnetic

d) Ferromagnetic View Answer Answer: b Explanation: The ferromagnetic materials are characterized by parallel alignment of magnetic dipole moments. Their susceptibility is very large. 2. The magnetic materials follow which law? a) Faraday’s law b) Ampere law c) Lenz law d) Curie Weiss law View Answer Answer: d Explanation: Generally, the ferromagnetic, paramagnetic and diamagnetic materials follow the Curie Weiss law, which relates the magnetization and the applied field. 3. Find the internal field when the applied field is 12 units, molecular field constant is 0.1 units and the magnetization is 74 units. a) 86 b) 62 c) 752 d) 19.4 View Answer Answer: d Explanation: From Curie law, the internal field of a magnetic material is given by H = Ho + χ M, where χ is the molecular field constant. Put χ = 0.1, M = 74 and Ho = 12, we get H = 12 + (0.1)74 = 19.4 units. 4. In which materials the magnetic anisotropy is followed? a) Diamagnetic b) Paramagnetic c) Ferromagnetic d) Ferromagnetic View Answer Answer: c

Explanation: In materials like iron, the magnetic properties depend on the direction in which they are measured. This is magnetic anisotropy. The material iron is a ferromagnetic material type. 5. Piezoelectric effect is analogous to which phenomenon? a) Electrostriction b) Magnetostriction c) Anisotropy d) Magnetization View Answer Answer: b Explanation: The piezoelectric effect is the mechanical strain caused on a material like quartz when subjected to an electric field. The same is observed in a ferromagnetic material call...