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SSP701S - SOLID STATE PHYSICS - 1ST OPP - JUNE 2022 |
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NAMIBIA UNIVERSITY
OF SCIENCE AND TECHNOLOGY
FACULTY OF HEALTH, APPLIED SCIENCES AND NATURAL RESOURCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION : BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
LEVEL: 7
COURSE CODE: SSP701S
COURSE NAME: SOLID STATE PHYSICS
SESSION: JUNE 2022
DURATION: 3 HOURS
PAPER: THEORY
MARKS: 100
FIRST OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S) | Prof Dipti R. Sahu
MODERATOR: | Dr Zivayi Chiguvare
INSTRUCTIONS
1. Answer all five questions.
2. Write clearly and neatly.
3. Number the answers clearly.
PERMISSIBLE MATERIALS
Non-programmable Calculators
THIS QUESTION PAPER CONSISTS OF 3 PAGES (Including this front page)
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Question 1
[20]
1.1 Calculate the lattice constant of Iron. Given density of iron 7.86 kg/cm?, atomic
(4)
weight of iron 55.85 and Avogadro’s number 6.023 x 107°/kmol.
1.2 Sketch the unit cell and show the following planes (112), (101), (123)
(6)
2.3. Show that the atomic packing factor for FCC and HCP metals are the same.
(10)
Question 2
[20]
2.1 What is Madelung constant? What is its significance?
(4)
2.2
How are secondary bonds formed? Give names of secondary bonds.
(6)
2.3
Compute the net potential energy of a simple Na*CI pair. The equilibrium distance between the
ions is 0.28nm. The potential energy due to repulsion between electron sis given by Ur=B/r® — (10)
Question 3
[20]
3.1 | What is meant by phonons? Do phonons have mass?
(4)
3.2. What is lattice wave? Calculate the value of cutoff frequency in a solid assuming a linear lattice. (6)
If velocity of sound in a solid is 3 x 10° m/s and Interatomic distance is 5 x 107° m.
3.3
What is Einstein theory of specific heat? Derive an expression for heat capacity of a
(10)
solid based on Einstein theory.
Question 4
[20]
4.1
Give the assumptions of the classical free electron theory.
(4)
4.2
State and explain Wiedemann-Franz law? Calculate Lorentz number, given the thermal and
electrical conductivities of Cu at 20°C are 390 WmK* and 5.87 x10’Q:'m? respectively
(6)
4.3
Using the free electron mode, derive an expression for electrical conductivity in metals.
(10)
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Question 5
[20]
5.1
Show that the probability of occupancy of energy level E by an electron
(4)
is 50% for E = Ef at temperature (T # OK).
5.2
Indicate on an energy level diagram the conduction and valence bands, donor and
acceptor states and the position of Fermi level for
(i) an intrinsic semiconductor.
(ii) a n-type semiconductor.
(iii) a p-type semiconductor.
(6)
5.3. Define mobility of a carrier of current. How is it related to the Hall coefficient? Is the mobility (10)
of an electron in the conduction band of a semiconductor the same as the mobility of an
electron (or hole) in the valence band? Give reason for your answer.
Given fundamental constants
Speed of light = 3x10°m/s
Planck constant = 6.626 x104 Js
Mass of electron= 9.1 x 10 kg
Charge of electron =1.6x10C
Avogadro number= 6.022 x 1073/mole
Boltzmann Constant =1.38 x 10°73 JK
a END