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PHYSICS HIGHER SECONDARY SECOND YEAR Textbook
physics second year - textbooks online and lecture notes of physics class 12 | pdf free download
VOLUME - I
Revised based on the recommendation of the
Textbook Development Committee
Untouchability is a sin
Untouchability is a crime
Untouchability is inhuman
COLLEGE ROAD, CHENNAI - 600 006c Government of Tamilnadu
First edition - 2005
Revised edition - 2007
Dr. S. GUNASEKARAN
Post Graduate and Research Department of Physics
Pachaiyappa’s College, Chennai - 600 030
P . SARVAJANA RAJAN
Selection Grade Lecturer in Physics P.G. Assistant in Physics
Govt. Hr. Sec. School
Nandanam, Chennai - 600 035 Kodambakkam, Chennai - 600 024
Selection Grade Lecturer in Physics
P.G. Assistant in Physics
Queen Mary’s College (Autonomous)
Govt. Girls’ Hr. Sec. School
Chennai - 600 004
Ashok Nagar, Chennai - 600 083
Dr. K. MANIMEGALAI
Reader in Physics
The Ethiraj College for Women
P.G. Assistant in Physics
Chennai - 600 008
Govt. Girls’ Hr. Sec. School
Tiruchengode - 637 211
Selection Grade Lecturer in Physics
Meenakshi College for Women
Dr. N. VIJAYAN
Kodambakkam, Chennai - 600 024
G. ANBALAGAN Zion Matric Hr. Sec. School
Lecturer in Physics
Aringnar Anna Govt. Arts College Chennai - 600 073
Dr. HEMAMALINI RAJAGOPAL
Senior Scale Lecturer in Physics
Queen Mary’s College (Autonomous)
Chennai - 600 004
Asst. Professor of Physics
S.R.M. Engineering College
S.R.M. Institute of Science and Technology
Kattankulathur - 603 203
Price : Rs.
This book has been prepared by the Directorate of School Education on behalf of
the Government of Tamilnadu
This book has been printed on 60 G.S.M paper
Printed by offset at :Preface
The most important and crucial stage of school education is the
higher secondary level. This is the transition level from a generalised
curriculum to a discipline-based curriculum.
In order to pursue their career in basic sciences and professional
courses, students take up Physics as one of the subjects. To provide
them sufficient background to meet the challenges of academic and
professional streams, the Physics textbook for Std. XII has been reformed,
updated and designed to include basic information on all topics.
Each chapter starts with an introduction, followed by subject matter.
All the topics are presented with clear and concise treatments. The
chapters end with solved problems and self evaluation questions.
Understanding the concepts is more important than memorising.
Hence it is intended to make the students understand the subject
thoroughly so that they can put forth their ideas clearly. In order to
make the learning of Physics more interesting, application of concepts in
real life situations are presented in this book.
Due importance has been given to develop in the students,
experimental and observation skills. Their learning experience would
make them to appreciate the role of Physics towards the improvement
of our society.
The following are the salient features of the text book.
N The data has been systematically updated.
N Figures are neatly presented.
N Self-evaluation questions (only samples) are included to sharpen
the reasoning ability of the student.
While preparing for the examination, students should not
restrict themselves, only to the questions/problems given in the self
evaluation. They must be prepared to answer the questions and
problems from the text/syllabus.
– Dr. S. Gunasekaran
IIISYLLABUS (180 periods)
UNIT – 1 ELECTROSTATICS (18 periods)
Frictional electricity, charges and their conservation; Coulomb’s
law – forces between two point electric charges. Forces between
multiple electric charges – superposition principle.
Electric field – Electric field due to a point charge, electric field
lines; Electric dipole, electric field intensity due to a dipole –behavior
of dipole in a uniform electric field – application of electric dipole in
Electric potential – potential difference – electric potential due to
a point charge and due a dipole. Equipotential surfaces – Electrical
potential energy of a system of two point charges.
Electric flux – Gauss’s theorem and its applications to find field
due to (1) infinitely long straight wire (2) uniformly charged infinite
plane sheet (3) two parallel sheets and (4) uniformly charged thin
spherical shell (inside and outside)
Electrostatic induction – capacitor and capacitance – Dielectric
and electric polarisation – parallel plate capacitor with and without
dielectric medium – applications of capacitor – energy stored in a
capacitor. Capacitors in series and in parallel – action of points –
Lightning arrester – Van de Graaff generator.
UNIT - 2 CURRENT ELECTRICITY (11 periods)
Electric current – flow of charges in a metallic conductor – Drift
velocity and mobility and their relation with electric current.
Ohm’s law, electrical resistance. V-I characteristics – Electrical
resistivity and conductivity. Classification of materials in terms of
conductivity – Superconductivity (elementary ideas) – Carbon resistors
– colour code for carbon resistors – Combination of resistors – series
and parallel – Temperature dependence of resistance – Internal
resistance of a cell – Potential difference and emf of a cell.
Kirchoff’s law – illustration by simple circuits – Wheatstone’s
Bridge and its application for temperature coefficient of resistance
measurement – Metrebridge – Special case of Wheatstone bridge –
Potentiometer – principle – comparing the emf of two cells.
Electric power – Chemical effect of current – Electro chemical
cells Primary (Voltaic, Lechlanche, Daniel) – Secondary – rechargeable
cell – lead acid accumulator.
IVUNIT – 3 EFFECTS OF ELECTRIC CURRENT (15 periods)
Heating effect. Joule’s law – Experimental verification.
Thermoelectric effects – Seebeck effect – Peltier effect – Thomson
effect – Thermocouple, thermoemf, neutral and inversion
Magnetic effect of electric current – Concept of magnetic field,
Oersted’s experiment – Biot-Savart law – Magnetic field due to an
infinitely long current carrying straight wire and circular coil –
Tangent galvanometer – Construction and working – Bar magnet as an
equivalent solenoid – magnetic field lines.
Ampere’s circuital law and its application.
Force on a moving charge in uniform magnetic field and electric
field – cyclotron – Force on current carrying conductor in a uniform
magnetic field, forces between two parallel current carrying conductors
– definition of ampere.
Torque experienced by a current loop in a uniform magnetic
field-moving coil galvanometer – Conversion to ammeter and voltmeter
– Current loop as a magnetic dipole and its magnetic dipole moment
– Magnetic dipole moment of a revolving electron.
UNIT – 4 ELECTROMAGNETIC INDUCTION AND
ALTERNATING CURRENT (14 periods)
Electromagnetic induction – Faraday’s law – induced emf and
current – Lenz’s law.
Self induction – Mutual induction – Self inductance of a long
solenoid – mutual inductance of two long solenoids.
Methods of inducing emf – (1) by changing magnetic induction
(2) by changing area enclosed by the coil and (3) by changing the
orientation of the coil (quantitative treatment) analytical treatment
can also be included.
AC generator – commercial generator. (Single phase, three
Eddy current – Applications – Transformer – Long distance
Alternating current – measurement of AC – AC circuit with
resistance – AC circuit with inductor – AC circuit with capacitor - LCR
series circuit – Resonance and Q – factor: power in AC circuits.
VUNIT–5 ELECTROMAGNETIC WAVES AND WAVE OPTICS
Electromagnetic waves and their characteristics –
Electromagnetic spectrum, Radio, microwaves, Infra red, visible, ultra
violet – X rays, gamma rays.
Emission and Absorption spectrum – Line, Band and continuous
spectra – Flourescence and phosphorescence.
Theories of light – Corpuscular – Wave – Electromagnetic and
Scattering of light – Rayleigh’s scattering – Tyndal scattering –
Raman effect – Raman spectrum – Blue colour of the sky and reddish
appearance of the sun at sunrise and sunset.
Wavefront and Huygen’s principle – Reflection, Total internal
reflection and refraction of plane wave at a plane surface using
Interference – Young’s double slit experiment and expression for
fringe width – coherent source - interference of light. Formation of
colours in thin films – analytical treatment – Newton’s rings.
Diffraction – differences between interference and diffraction of
light – diffraction grating.
Polarisation of light waves – polarisation by reflection –
Brewster’s law - double refraction - nicol prism – uses of plane
polarised light and polaroids – rotatory polarisation – polarimeter
UNIT – 6 ATOMIC PHYSICS (16 periods)
Atomic structure – discovery of the electron – specific charge
(Thomson’s method) and charge of the electron (Millikan’s oil drop
method) – alpha scattering – Rutherford’s atom model.
Bohr’s model – energy quantisation – energy and wave number
expression – Hydrogen spectrum – energy level diagrams – sodium and
mercury spectra - excitation and ionization potentials. Sommerfeld’s
X-rays – production, properties, detection, absorption, diffraction
of X-rays – Laue’s experiment – Bragg’s law, Bragg’s X-ray
spectrometer – X-ray spectra – continuous and characteristic X–ray
spectrum – Mosley’s law and atomic number.
Masers and Lasers – spontaneous and stimulated emission –
normal population and population inversion – Ruby laser, He–Ne laser
– properties and applications of laser light – holography
VIUNIT – 7 DUAL NATURE OF RADIATION AND MATTER –
RELATIVITY (10 periods)
Photoelectric effect – Light waves and photons – Einstein’s photo
– electric equation – laws of photo – electric emission – particle nature
of energy – photoelectric equation – work function – photo cells and
Matter waves – wave mechanical concept of the atom – wave
nature of particles – De–Broglie relation – De–Broglie wave length of
an electron – electron microscope.
Concept of space, mass, time – Frame of references. Special
theory of relativity – Relativity of length, time and mass with velocity
– (E = mc ).
UNIT – 8 NUCLEAR PHYSICS (14 periods)
Nuclear properties – nuclear Radii, masses, binding energy,
density, charge – isotopes, isobars and isotones – Nuclear mass defect
– binding energy. Stability of nuclei-Bain bridge mass spectrometer.
Nature of nuclear forces – Neutron – discovery – properties –
artificial transmutation – particle accelerator
Radioactivity – alpha, beta and gamma radiations and their
properties, α-decay, β-decay and γ-decay – Radioactive decay law – half
life – mean life. Artificial radioactivity – radio isotopes – effects and
uses Geiger – Muller counter.
Radio carbon dating – biological radiation hazards
Nuclear fission – chain reaction – atom bomb – nuclear reactor
– nuclear fusion – Hydrogen bomb – cosmic rays – elementary
UNIT – 9 SEMICONDUCTOR DEVICES AND THEIR APPLICATIONS
Semiconductor theory – energy band in solids – difference
between metals, insulators and semiconductors based on band theory
– semiconductor doping – Intrinsic and Extrinsic semi conductors.
Formation of P-N Junction – Barrier potential and depletion
layer. – P-N Junction diode – Forward and reverse bias characteristics
– diode as a rectifier – zener diode. Zener diode as a voltage regulator
VIIJunction transistors – characteristics – transistor as a switch –
transistor as an amplifier – transistor biasing – RC, LC coupled and
direct coupling in amplifier – feeback amplifier – positive and negative
feed back – advantages of negative feedback amplifier – oscillator –
condition for oscillations – LC circuit – Colpitt oscillator.
Logic gates – NOT, OR, AND, EXOR using discret components –
NAND and NOR gates as universal gates – integrated circuits.
Laws and theorems of Boolean’s algebra – operational amplifier –
parameters – pin-out configuration – Basic applications. Inverting
amplifier. Non-inverting amplifier – summing and difference
Measuring Instruments – Cathode Ray oscillocope – Principle –
Functional units – uses. Multimeter – construction and uses.
UNIT – 10 COMMUNICATION SYSTEMS (15 periods)
Modes of propagation, ground wave – sky wave propagation.
Amplitude modulation, merits and demerits – applications –
frequency modulation – advantages and applications – phase
Antennas and directivity.
Radio transmission and reception – AM and FM –
T.V.transmission and reception – scanning and synchronising.
Vidicon (camera tube) and picture tube – block diagram of a
monochrome TV transmitter and receiver circuits.
Radar – principle – applications.
Digital communication – data transmission and reception –
principles of fax, modem, satellite communication – wire, cable and
Fibre - optical communication.
VIIIEXPERIMENTS (12 × 2 = 24 periods)
1. To determine the refractive index of the material of the prism by
finding angle of prism and angle of minimum deviation using a
2. To determine wavelengths of a composite light using a diffraction
grating and a spectrometer by normal incidence method (By
3. To determine the radius of curvature of the given convex lens
using Newton’s rings experiment.
4. To find resistance of a given wire using a metre bridge and hence
determine the specific resistance of the material.
5. To compare the emf’s of two primary cells using potentiometer.
6. To determine the value of the horizontal component of the magnetic
induction of the earth’s magnetic field, using tangent galvanometer.
7. To determine the magnetic field at a point on the axis of a circular
8. To find the frequency of the alternating current (a.c) mains using
a sonometer wire.
9. (a) To draw the characteristic curve of a p-n junction diode in
forward bias and to determine its forward resistance.
(b) To draw the characteristic curve of a Zener diode and to
determine its reverse breakdown voltage.
10. To study the characteristics of a common emitter NPN transistor
and to find out its input, output impedances and current gain.
11. Construct a basic amplifier (OP amp) using IC 741 (inverting, non
12. Study of basic logic gates using integrated circuits NOT, AND, OR,
NAND, NOR and EX-OR gates.
1 Electrostatics 1
2 Current Electricity 53
3 Effects of Electric Current 88
4 Electromagnetic Induction
and Alternating Current 134
5 Electromagnetic Waves and
Wave Optics 178
Logarithmic and other tables 228
(Unit 6 to 10 continues in Volume II)
Electrostatics is the branch of Physics, which deals with static
electric charges or charges at rest. In this chapter, we shall study the
basic phenomena about static electric charges. The charges in a
electrostatic field are analogous to masses in a gravitational field. These
charges have forces acting on them and hence possess potential energy.
The ideas are widely used in many branches of electricity and in the
theory of atom.
1.1 Electrostatics – frictional electricity
In 600 B.C., Thales, a Greek Philosopher observed that, when a
piece of amber is rubbed with fur, it acquires the property of attracting
light objects like bits of paper. In the 17 century, William Gilbert
discovered that, glass, ebonite etc, also exhibit this property, when
rubbed with suitable materials.
The substances which acquire charges on rubbing are said to be
‘electrified’ or charged. These terms are derived from the Greek word
elektron, meaning amber. The electricity produced by friction is called
frictional electricity. If the charges in a body do not move, then, the
frictional electricity is also known as Static Electricity.
1.1.1 Two kinds of charges
(i) If a glass rod is rubbed with a silk cloth, it acquires positive
charge while the silk cloth acquires an equal amount of negative charge.
(ii) If an ebonite rod is rubbed with fur, it becomes negatively
charged, while the fur acquires equal amount of positive charge. This
classification of positive and negative charges were termed by American
scientist, Benjamin Franklin.
Thus, charging a rod by rubbing does not create electricity, but
simply transfers or redistributes the charges in a material.
1.1.2 Like charges repel and unlike charges attract each other
– experimental verification.
A charged glass rod is suspended by a silk thread, such that it
swings horizontally. Now another charged glass rod is brought near the
end of the suspended glass rod. It is found that the ends of the two
rods repel each other (Fig 1.1). However, if a charged ebonite rod is
brought near the end of the suspended rod, the two rods attract each
other (Fig 1.2). The above experiment shows that like charges repel and
unlike charges attract each other.
Fig 1.2 Two charged rods
Fig. 1.1 Two charged rods
of opposite sign
of same sign
The property of attraction and repulsion between charged bodies
have many applications such as electrostatic paint spraying, powder
coating, fly−ash collection in chimneys, ink−jet printing and photostat
copying (Xerox) etc.
1.1.3 Conductors and Insulators
According to the electrostatic behaviour, materials are divided
into two categories : conductors and insulators (dielectrics). Bodies
which allow the charges to pass through are called conductors. e.g.
metals, human body, Earth etc. Bodies which do not allow the charges
to pass through are called insulators. e.g. glass, mica, ebonite, plastic
- - - - -
+ + +++
+++++++ 1.1.4 Basic properties of electric charge
(i) Quantisation of electric charge
The fundamental unit of electric charge (e) is the charge
carried by the electron and its unit is coulomb. e has the magnitude
1.6 × 10 C.
In nature, the electric charge of any system is always an integral
multiple of the least amount of charge. It means that the quantity can
take only one of the discrete set of values. The charge, q = ne where
n is an integer.
(ii) Conservation of electric charge
Electric charges can neither be created nor destroyed. According
to the law of conservation of electric charge, the total charge in an
isolated system always remains constant. But the charges can be
transferred from one part of the system to another, such that the total
charge always remains conserved. For example, Uranium ( U ) can
decay by emitting an alpha particle ( He nucleus) and transforming to
thorium ( Th ).
238 234 4
U −−−−→ Th + He
92 90 2
Total charge before decay = +92e, total charge after decay = 90e + 2e.
Hence, the total charge is conserved. i.e. it remains constant.
(iii) Additive nature of charge
The total electric charge of a system is equal to the algebraic sum
of electric charges located in the system. For example, if two charged
bodies of charges +2q, −5q are brought in contact, the total charge of
the system is –3q.
1.1.5 Coulomb’s law
The force between two charged bodies was studied by Coulomb in
Coulomb’s law states that the force of attraction or repulsion
between two point charges is directly proportional to the product of the
charges and inversely proportional to the square of the distance between
them. The direction of forces is along
the line joining the two point charges.
Let q and q be two point charges
Fig 1.3a Coulomb forces
placed in air or vacuum at a distance r
apart (Fig. 1.3a). Then, according to
F α or F = k
where k is a constant of proportionality. In air or vacuum,
k = , where ε is the permittivity of free space (i.e., vacuum) and
−12 2 −1 −2
the value of ε is 8.854 × 10 C N m .
F = …(1)
9 2 −2
and = 9 × 10 N m C
In the above equation, if q = q = 1C and r = 1m then,
F = (9 × 10 ) = 9 × 10 N
One Coulomb is defined as the quantity of charge, which when
placed at a distance of 1 metre in air or vacuum from an equal and
similar charge, experiences a repulsive force of 9 × 10 N.
If the charges are situated in a medium of permittivity ε, then the
magnitude of the force between them will be,
F = …(2)
Dividing equation (1) by (2)
The ratio = ε , is called the relative permittivity or dielectric
constant of the medium. The value of ε for air or vacuum is 1.
∴ ε = ε ε
Since F = , the force between two point charges depends on
the nature of the medium in which the two charges are situated.
Coulomb’s law – vector form
If F is the force exerted on charge
q by charge q (Fig.1.3b),
F r q
= k q
21 12 1
where r is the unit vector
from q to q .
Fig 1.3b Coulomb’s law in
If F is the force exerted on
12 vector form
q due to q ,
F = r
where r is the unit vector from q to q .
21 2 1
Both r and r have the same magnitude, and are oppositely
∴ F 2 (– r )
or F 2 r
or F = – F
So, the forces exerted by charges on each other are equal in
magnitude and opposite in direction.
51.1.6 Principle of Superposition
The principle of superposition is to calculate the electric force
experienced by a charge q due to other charges q , q ……. q .
1 2 3 n
The total force on a given charge is the vector sum of the forces
exerted on it due to all other charges.
The force on q due to q
12 4πε 21
Similarly, force on q due to q
13 4πε 31
The total force F on the charge q by all other charges is,
→ → → → →
F = F + F + F F
1 12 13 14 ......... + 1n
qq qq q q
12 13 1 n
rr++ ....... r
21 31 n1
F⎢⎥ 22 2
ο⎣⎦ 21 31 n1
1.2 Electric Field
Electric field due to a charge is the space around the test charge
in which it experiences a force. The presence of an electric field
around a charge cannot be detected unless another charge is brought
When a test charge q is placed near a charge q, which is the
source of electric field, an electrostatic force F will act on the test
Electric Field Intensity (E)
Electric field at a point is measured in terms of electric field
intensity. Electric field intensity at a point, in an electric field is defined
as the force experienced by a unit positive charge kept at that point.
It is a vector quantity. . The unit of electric field intensity
is N C .
The electric field intensity is also referred as electric field strength
or simply electric field. So, the force exerted by an electric field on a
charge is F = q E.
1.2.1 Electric field due to a point charge
Let q be the point charge +q +q
placed at O in air (Fig.1.4). A test
charge q is placed at P at a
distance r from q. According to
Fig 1.4 Electric field due to a
Coulomb’s law, the force acting on
q due to q is
The electric field at a point P is, by definition, the force per unit
The direction of E is along the line joining O and P, pointing away
from q, if q is positive and towards q, if q is negative.
In vector notation E r, where r is a unit vector pointing
away from q.
1.2.2 Electric field due to system of charges
If there are a number of stationary charges, the net electric field
(intensity) at a point is the vector sum of the individual electric fields
due to each charge.
→ → → → →
E = E + E + E ...... E
1 2 3 n
q q q
1 2 3
rr ++ r +.........
⎢⎥ 22 2
o⎣⎦ 12 3
1.2.3 Electric lines of force
The concept of field lines was introduced by Michael Faraday as
an aid in visualizing electric and magnetic fields.
Electric line of force is an imaginary straight or curved path along
which a unit positive charge tends to move in an electric field.
The electric field due to simple arrangements of point charges are
shown in Fig 1.5.
(a) (b) (c)
Isolated charge Unlike charges Like charges
Fig1.5 Lines of Forces
Properties of lines of forces:
(i) Lines of force start from positive charge and terminate at negative
(ii) Lines of force never intersect.
(iii) The tangent to a line of force at any point gives the direction of
the electric field (E) at that point.
(iv) The number of lines per unit area, through a plane at right angles
to the lines, is proportional to the magnitude of E. This means
that, where the lines of force are close together, E is large and
where they are far apart, E is small.
(v) Each unit positive charge gives rise to lines of force in free
space. Hence number of lines of force originating from a point
charge q is N = in free space.
81.2.4 Electric dipole and electric dipole moment
Two equal and opposite charges
separated by a very small distance p
constitute an electric dipole.
Water, ammonia, carbon−dioxide and
Fig 1.6 Electric dipole
chloroform molecules are some examples
of permanent electric dipoles. These
molecules behave like electric dipole, because the centres of positive
and negative charge do not coincide and are separated by a small
Two point charges +q and –q are kept at a distance 2d apart
(Fig.1.6). The magnitude of the dipole moment is given by the product
of the magnitude of the one of the charges and the distance between
∴ Electric dipole moment, p = q2d or 2qd.
It is a vector quantity and acts from –q to +q. The unit of dipole
moment is Cm.
1.2.5 Electric field due to an electric dipole at a point on its
AB is an electric dipole of two point charges –q and +q separated
by a small distance 2d (Fig 1.7). P is a point along the axial line of the
dipole at a distance r from the midpoint O of the electric dipole.
Fig 1.7 Electric field at a point on the axial line
The electric field at the point P due to +q placed at B is,
E = (along BP)
() rd −
9The electric field at the point P due to –q placed at A is,
E = (along PA)
() rd +
E and E act in opposite directions.
Therefore, the magnitude of resultant electric field (E) acts in the
direction of the vector with a greater magnitude. The resultant electric
field at P is,
E = E + (−E )
E = ⎢⎥ along BP.
44 πε πε
() rd−+(r d)
E = ⎢⎥ along BP
4πε () rd−+(r d)
E = ⎢⎥along BP.
4πε() rd −
If the point P is far away from the dipole, then d r
qr44 d q d
∴ E =
44 πε πε
E = along BP.
Electric dipole moment p = q x 2d
E acts in the direction of dipole moment.