1. Burger vectors are relevant to which of the following crystalline defects?
a) Point defects
b) Line defects
c) Interfacial defects
d) Bulk defects
Explanation: Burger vector denotes the magnitude and direction of a line defect.
2. Pores & cracks in crystalline solids can be classified as bulk defects.
a) True
b) False
Explanation: Pores and cracks are not localized to a particular point or edge, but have sizes much larger than atomic dimensions.
3. Ferromagnetic material shows strong para-magnetic behaviour due to the formation of domains. These domains belong to:
a) Point defects
b) Linear defects
c) Interfacial defects
d) Bulk defects
Explanation: In ferromagnetic materials, the alignment of magnetic dipoles vary across domain walls. These walls spread across large surfaces but have negligible thickness.
4. Electrical conductivity of the specimen is a requirement for which of the following microscopic examination techniques?
a) Optical microscopy
b) Transmission electron microscopy
c) Scanning electron microscopy
d) Scanning probe microscopy
Explanation: Non-conducting specimen will develop electrostatic charge due to an incident electron beam. This field tends to produce faults in the signal interpretation.
5. Which of the following point defects is non-stoichiometric in nature?
a) Schottky defect
b) Metal excess defect
c) Interstitial defect
d) Impurity defect
Explanation: When alkali halides are heated in an atmosphere of the constituent metal, halide ions diffuse to the surface to react with the vapour particles. This results in excess of cations over anions.
6. The solubility of solute in a solvent in a solid solution is governed by Hume-Rothery rules. The solubility is more if:
a) radii of solute are much smaller than that of solvent
b) solute an solvent have a similar crystal structure
c) solute has low valence
d) all of the mentioned
Explanation: For high solubility, the solute-solvent pair should have similar radii, crystal structure, and electronegativity. Moreover, for other factors being equal, a solute with higher valence is more soluble than one having lower valence.
7. Which type of defect are point defects?
a) One dimensional defect
b) Zero dimensional defect
c) Two dimensional defect
d) Three dimensional defect
Explanation: Point defects are zero dimensional defects as they cannot extend in any direction in space. Point defects occur where an atom is missing or misplaced in a crystal lattice. The limit of the size of point defect is not defined.
8. Which of the following point defects can be attributed to from the below options?
i) Stress Fields
ii) Strain fields
iii) Charge
iv) Current
a) i) and ii)
b) ii) and iv)
c) i) and iii)
d) ii) and iv)
Explanation: Stress fields are produced due to point dislocation and charges are needed for point dislocation. When an atom dislocates from its original position to an interstitial position or it is completely removed from the lattice, hence creating stress fields.
9. Which is not a name given to vacancy in some ionic solid?
a) H-center
b) F-center
c) Color center
d) Luminescence center
Explanation: Other than H-center which is used when a halogen occupies the interstitial position, all the other terms are used for a vacancy in ionic solid. For some ionic solid when there is a vacancy in crystal, an F-center or color enter or luminescence center is formed due to which the ionic solid exhibits different colors.
10. If the number of F-centers are more, the color of the compound gets more intense.
a) True
b) False
Explanation: When the number of F-center increases, more light is absorbed from the visible spectra and intense color is obtained. By the same logic when the number of F-centers are less, colors are less intense.