Engineering Physics

By Dr. S.G Ibrahim

It has been recognised from the beginning that the most successful research of technology is predicated on a greater comprehension of scientific principles. We are delighted to introduce this Engineering Physics book to science and engineering students. This book covers the entire engineering physics syllabus as provided by Sant Gadge Baba Amravati University. This book includes theoretical questions, multiple choice questions, solved numerical problems, and practice numerical problems with solutions to help students to gain confidence and motivate them to study extensively. It is sincerely hoped that both students and teachers would find this book beneficial.

• Language: English
• Publisher: Famian
• Release date: Jan 27, 2022
• ISBN: 9798201135683

Book preview

Acknowledgement

I would like to thank everyone at Prof. Ram Meghe College of Engineering and Management, Badnera, especially all Management members, Principal, Staff and Famian Publication. I would also like to thank my mother, wife, and brothers, whose unwavering love and compassion have been continual source of inspiration.

I would like to dedicate my work to the memories of my father Late S.S. Ibrahim.

Dr. S. G. Ibrahim

Preface

It has been recognised from the beginning that the most successful research of technology is predicated on a greater comprehension of scientific principles. I am delighted to introduce this Engineering Physics book to science and engineering students.

The book covers the entire engineering physics syllabus as provided by Sant Gadge Baba Amravati University. The book includes theoretical questions, multiple choice questions, solved numerical problems, and practice numerical problems with solutions to help students to gain confidence and motivate them to study extensively.

It is sincerely hoped that both students and teachers would find this book beneficial. Any ideas for improving the book from teachers and students would be much appreciated by the author.

REVISED SYLLABUS

(As per as S.G.B.A.U, Amravati)

Chapter I: Solid State Physics

Classification of solids on the basis of energy band diagram, Covalent bonds, bound & free electrons, holes, electron and hole mobilities, Intrinsic and Extrinsic semiconductors, and energy band diagram for semi-conductors. Fermi and Impurity levels, semiconductor conductivity with derivation, Law of mass action (only statement), P-N junction diode, Zener diode, Light Emitting Diode, Hall Effect.

Chapter II: Modern Physics

Planck’s hypothesis, properties of Photons, Compton effect, De-Broglie’s concept of matter waves, wave particle duality, Heisenberg’s Uncertainty Principle (statement and derivation), applications of uncertainty principle (electrons cannot exist in the nucleus and binding energy of electron in atom), Time energy uncertainty relation, wave function and its significance.

Chapter III: Electric and Magnetic Fields

Motion of electron in uniform transverse electric field and transverse magnetic field, velocity selector (energy filter), positive rays, Bainbridge mass spectrograph, Cathode ray oscilloscope: block diagram and working of each block.

Chapter IV: Interference and Diffraction

Fundamental condition of interference, thin film interference due to reflected light, Newton’s ring; equation for radius of bright and dark rings, determination of wavelength, R.I. of medium using Newton’s ring. Fresnel and Fraunhofer class of diffraction, single slit diffraction, plane transmission grating; construction and determination of wavelength of light using grating, dispersive power of grating.

Chapter V: Fibre Optics and LASER

Principle and construction of optical fibre, acceptance angle and acceptance cone numerical aperture, types of optical fibres and refractive index profile, attenuation in optical fibres, different mechanisms of attenuation, application of optical fibres. LASER: spontaneous and stimulated emission of radiation, Pumping, Optical Pumping, Ruby LASER (Construction and Working), Characteristics & Applications of Laser in Industrial, Medical and Scientific field.

Chapter VI: Acoustics, Ultrasonic and Fluid dynamics

Acoustics: Sound waves, reflection of sound waves, defects due to reflected sound (echo and reverberation), absorption of sound, Sabine’s formula for reverberation of time, Factors affecting architectural acoustics and its remedies. Ultrasonic: Ultrasonic waves, Production of Ultrasonic waves (piezo-electric and magnetostriction methods), properties of Ultrasonic waves and applications. Fluid dynamics: Viscosity, Stokes’s law, liquid flow (streamline and turbulent), flow of liquids through a capillary tube (Poiseuille’s equation), Continuity equation, Bernoulli’s Equation (only derivation).

Contents

Energy Band in Solid

Consider an isolated silicon atom; its energy levels are quantized. When two identical atoms are brought closer together, the quantized energy levels hybridize and split into two different levels because of the mutual interaction of the two atoms. More generally, when N atoms are moved closer, until they reach the equilibrium inter-atomic distance d, the energy levels split into N levels. These N levels are very close to each other if N is large (which is the case in a crystal) so that they eventually form a continuous energy band. Let's now consider silicon atoms arranged in a periodic lattice, but with a very large lattice parameter (or inter-atomic distance), in order to first consider each atom as isolated. The two levels with the highest energy are labeled E1 and E2. Now let's shrink homothetically the atom lattice: energy levels split and form two continuous bands known as the conduction band (CB) and the valence band (VB), Figure below shows the formation of these bands as a function of the inter-atomic distance.

Formation of energy bands for electrons in a silicon crystal with a diamond-type lattice structure

In a silicon crystal (d=2.35Å), two continuous energy bands exist (CB and VB), separated by a forbidden band, which is not accessible for electrons. This forbidden region is called the forbidden gap and its width Eg is a characteristic of the material. The lowest energy level of the conduction band is denoted by (Ec) and the highest energy level of the valence band is denoted by (Ev) so that we have the relationship Eg=Ec­Ev. The conduction and valence bands CB and VB represent the energies accessible to electrons, or the energies of the states potentially occupied by electrons, they do not provide any information about the effective occupation of the energy states by electrons.

Conduction band, Forbidden band and Valence band

The energy bands are classified as:

Valence band

Forbidden Energy Gap

Conduction Band

Valence Band:

There are multiple ranges of energies present in the solid at absolute zero temperature, and the band created by the highest range of energies is called the valence band, which is filled with valence electrons. When atoms are brought closer together to create a solid, quantum mechanical forces cause the discrete energy levels to be disturbed, and many electrons in the group of the individual atom occupy a band of levels in the solid, which is referred to as the valence band. The electrons in the outermost shell create this band. It lies beneath the Fermi level. The energy of electrons in the valence band is lower than that of electrons in the conduction band. Electrons in the outermost shell form this band. The electrons in the valence band in atoms are loosely connected to the nucleus. The ability of a material to transport electrons from the valence band to the conduction band determines its electrical conductivity.

Forbidden Energy Level:

Fermi energy level is a term that refers to the forbidden energy gap. Due to quantization energy, it is the electronic energy band in which no electron states exist. The prohibited energy band or forbidden gap is the band that results from separating the conduction and valence bands. Because there is no energy state in this region in materials, electrons do not remain in the forbidden gap. The major factor, i.e., the electrical conductivity of the material, can be determined with the use of forbidden gap.

Conduction Band:

The conduction band is the energy band created by the energy levels of free electrons. The conduction band is either empty or partially filled,