Objective

I. Starting in 2015 E.C., the Ethiopian ministry of

education will administer an exit test to every student
in the graduating class. In order for students in the
B.Sc. program of the graduating class of physics to
develop full confidence for the actual national exit test
(accreditation), this model exam has been prepared.
II. These questions aren’t intended to be solved or
answered instantly; rather, they’re designed so that
students must read a little bit and engage in discussion
to help prepare them for the real tests in advance.
G.Kunsa Haho H.
Email: kunsahaho@gmail.com
January 11, 2023

1
 Part I. CHOOSE THE BEST ANSWER FROM THE GIVEN
ALTERNATIVES.

1. The following group of materials are not characterized by an ordered arrangement of

their ions, atoms or molecules.
A. Monocrystalline B. Polycrystalline C. Crystalline D. Amorphous
2. Basis in the crystal lattice can be one of the following except.
A. Atoms B. Molecules C. Polymers D. Carbonates
3. The type of cell that contains a single point in a direct lattice is
A. Primitive cell B. Unit cell C. Conventional unit cell D. Wigner-Seitz cell
4. The imaginary array of points arranged in space are
A. Basis B. Lattices C. Crystal structure D. Ideal crystal
5. The total number of Bravais lattices in three dimension with two lattice points are
A. 6 B. 5 C. 2 D. 3
6. Which of the following crystal system contains the highest number of in Bravias lattices
three dimension
A. Cubic B. Orthorombic C. Tetragonal D. Orthogonal
7. Which of the following crystal system contains the highest number of in Bravias lattices
two dimension
A. Square B. Hexagonal C. Rectangular D. Oblique
8. The following crystal systems are regarded to as general type of crystal system in a the
two and three dimensions respectively.
A. Square and Cubic B. Oblique and Triclinic C. Hexagonal and Hexagonal
D. Rectangular and Tetragonal
9. One of the following symmetry element is not a point group symmetry operation element.
A. Translation B. Reflection C. Rotation D. Inversion
10. In a crystal lattice, for every point in a position r, there exist a lattice point at -r. The
symmetry operation in this crystal lattice is
A. Translation B. Reflection C. Rotation D. Inversion
11. The total number of space group in a crystal system in three dimension is
A. 32 B. 230 C. 14 D. 7
12. One of the following folded axis of rotation does not give lattice structure that goes in
to itself
A. 3 B. 1 C. 5 D. 6
13. The following crystal systems has only primitive unit cell except
A. Hexagonal B. Cubic C. Trigonal D. Triclinic
14. It has least packing fraction of atoms with respect to others
A. Diamond B. Simple cubic C. Face centered cubic D. HCP structure
15. The sodium metal crystallizes in a body centered cubic lattice with lattice constant of
4.29Å. What is the atomic radius of sodium metal?
A. 1.76 Å B. 1.86 Å C. 0.86 Å D. 0.76Å
2
16. If the plane intercepts the x,y,and z axis at 4, 3
and -2 ,then the miller index for this
plane is
A. [162̄] B. (162̄) C. ⟨162̄⟩ D. {162̄}
17. The elements such as He, Be, Zn and Ge etc are crystallize in
A. Wurtizite B. diamond structure C. Zinc Blended D. HCP structure
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18. Lead is a face centered cubic with an atomic radius of 0.1746nm. What is the lattice
constant of lead?
A. 0.734nm B. 0.493 nm C. 3.64nm D. 2.5nm

19. In above question what is the distances of (220) planes

A. 0.2465nm B. 0.226nm C. 0.830nm D. 0.174 nm

20. If the primitive translational vector of two directional lattice are: ⃗a1 = 2ĵ + ĵ and
⃗a2 = 2ĵ. What are the primitive translational vectors of its reciprocal lattices ⃗b1 and ⃗b2
respectively?
A. 3π î and π(î − ĵ)
B. π î and π2 (−î + 2ĵ)
C. 2π î and π(−î + 2ĵ)
π 3π
D. 2
(î + ĵ) and 2
(−î + 2ĵ)

21. It is the smallest volume entirely enclosed by planes that are the perpendicular bisectors
of the reciprocal lattice vectors drawn from the origin.
A. Iterplanar distance B. Brillouin zone C. Extended region D. Periodic Region

22. The statement below is describes the characteristics of x-ray diffraction in crystals ex-
cept
A. It uses to know unit cells types in crystal
B. It uses to identify amorphous and crystalline materials
C. It uses to differentiate atomic isotopes
D. It uses to identify phases of solids

23. The shape of first Brillouin zone in FCC lattice is

A. Simple cubic B. Turncated octahedron C. Rhombic dodecahedron D. Tetra-
hedron

24. Which types of radiations are used to study the crystal structures
A. X-rays B. UV-rays C. Gamma rays D. Visible light

25. If a is a lattice constant and λ is the wave length of x-rays the for no diffraction to occur
the condition is
A. a < λ < 2a B. λ < a C. λ > 2a D. λ > a

26. The Bragg law in terms of the reciprocal lattice vector G is

A. 2K.G + K 2 = 0
B. G.G + 2K.2K = 0
C. 2K.G + G2 = 0
D. 2G.G + K.K = 0

27. One of the following is not a liquid crystal

A. Nematics B. Cholesterics C. Smectics D. Silicenes

28. The following are the primary type of bondings in solids except
A. Hydrogen bonding
B. Electrostatic bonding
C. Metallic bonding
D. Covalent bonding

29. The type of bonds that most likely to produce a semiconductor materials is
A. Ionic B. Van der waals C. Covalent D. Metallic

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30. One of the following is not categorized as a molecular crystals

A. Oxygen B. Nitrogen C. Boron D. Helium

⃗ values for
31. In a case of monoatomic lattice vibration in a one dimension the range of K
the first Brillouin zone is (a is lattice constant)

⃗ ≤
A. 0 ≤ K π
B. −2π ⃗ ≤
≤K 2π ⃗ ≤
C. − πa ≤ K π ⃗ ≤
D. 0 ≤ K 2π
a a a a a

32. If the velocity of the moving wave not depend on the frequency then the solid is
A. Non-dispersive B. Crystalline C. Dispersive D. Non-crystalline

33. A phonon is a quanta of the energy of

A. Electromagnetic wave
B. Elastic wave
C. Collective electron wave
D. Magnetization wave

34. One of the following is not true about the case of long wave length limit of the monoatomic
vibration in one dimension
A. It refers to the low frequency limit
B. The group velocity is equal to phase velocity
C. The material acts as a dispersive medium
D. It refers to the condition that wave vector approaches to zero

35. Among the following whose theory of specific heat capacity of the solid predicts better
values both at low and high temperature is
A. Dulong and Petit B. Enstein C. Debye D. Plancks

36. One of the international notation of the space group of cubic crystal system is 4̄3m.Which
one is correct meaning of this notation
A. Three folded axis transnational symmetry
B. It has inversion symmetry on three folded axis
C. Three folded axis rotational symmetry
D. It has reflection symmetry

37. What will happen to the conductivity of conductors, semiconductors and insulators as
the they are exposed to the higher temperatures?
A. It increases in conductors
B. It decreases in semiconductors
C. It increases in insulators
D. It is impossible to determine

38. Find One of the following is not true about holes and electrons in a band structure
A. Holes are the deficiency of electrons in a valance band
B. Mass of holes are greater than that of electrons
C. There are conditions in which electron mass is greater that of holes
D. Holes are at lower energy than electrons

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39. In which type of semiconductors the number of the holes and electrons are equal?
A. Intrinsic semiconductors
B. N-type semiconductors
C. Extrinsic semiconductors
D. P-type semiconductors

40. What will happen to Fermi energy of conductors as temperature increases

A. It increases
B. It does not depend on temperature
C. It decreases
D. It is impossible to determine

41. By Considering the density of states of electrons in a metals as the function of energy,
what will happen to density of states as the temperature of material increasing
A. It increases
B. It does not depend on temperature
C. It decreases
D. It decreases below the Fermi level and increases above Fermi level

42. Which one is true about the mass of electrons

A. The effective mass of electron is always positive
B. Mass of free electron is always greater than its effective mass
C. Effective mass depends on wave vector but mass of free electron depend on
energy
D. Mass of free electron can be equal to its effective mass

43. The following equation is regarding the Fermi level (EF ) of p-type semiconductors is
true(Hint: Ec is conduction band edge and Ev is valance band edge)?
A. EF < Ec +E
2
V
B. EF = Ec +E
2
V
C. EF > Ec +E
2
V
D. EF = Ec = EV

44. Which one is not correct about the graphene?

A. It is an isotope of carbon and stronger than diamond
B. It is a two dimensional crystal with hexagonal lattice
C. It is a semi-metallic material with a covalent bonds
D. It is a semiconductor material with a perfect conductivity

45. Which of the following best describes what a derivative is?

A. The slope of the tangent line or instantaneous rate of change
B. The slope of the secant line or average rate of change
C. The equation of a tangent line at a point
D. The equation of the tangent line anywhere on the curve
E. none of the above

46. If the probability of finding an electron in silver is 10% whose energy is 1% above the
Fermi-energy. Then what will be the expected temperature? (use: the Fermi energy of
the silver is 5.5eV and Boltzmann constant, kB = 1.38x10−23 J/K)
A. 700K
B. 26K
C. 290K
D. 50K

47. In above question, what is the probability of finding an electron in silver, if the electron
energy is EF + kB T , where, kB is Boltzmann constant and T is a temperature in K.

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A. 0.190
B. 0.269
C. 0.546
D. 1

48. The electronic heat capacity of the metal dependent on the temperature,T and it is
proportional to
−2
A. T 3

B. T 2
C. T
1
D. T 2

49. One of the following particle can not be identified as a Fermion

A. Electron
B. Neutron
C. Proton
D. Phonon

50. The Fermi energy in a metals at 0K is proportional to electron density (n), according
to
−3
A. n 2

B. n2
2
C. n 3
D. n

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