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Challenges and Evaluation in Physics N.K. Sehgal November 2013.

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1 Challenges and Evaluation in Physics N.K. Sehgal November 2013

2 Physics The subject of Physics is a beautiful amalgamation of philosophical thinking, reality and practical utility. It aims to understand and explain a vast variety of natural phenomenon and observations, in the physical world, through a relatively small number of principals, rules and laws. Nature and physical universe do not appear to yield their secrets readily. However, the human mind has always struggled and tried to gain an understanding, and perhaps even a mastery, over nature. The curiosity to understand nature and natural phenomenon, and to seek explanations, of the vast variety of everyday observations and happenings, has been the guiding and motivating force behind all sciences in general and physics in particular.

3 Physics In broad terms, one may say that the role of physics is to provide a logically consistent picture of universe that is in agreement with experience, i.e., a picture that, in a way, saves the phenomenon. We may consider Physics as the branch of science concerned with the discovery, and logical characterization, of universal laws which govern matter, energy, space and time.

4 Physics The teaching of physics is both a challenge and an opportunity. The challenge lies in dispelling the common notion, and fear, that Physics is perhaps the most difficult of all sciences. The opportunity lies in making the students realize that the basic principles of physics have helped mankind to develop,and use, the vast variety of devices - heat engines, electricity generators, wireless communication, lasers, television, air conditioners, computers, robots, ultrasound, MIR and PET imaging, mobile phones nuclear reactors and artificial satellites, to name but a few - that have changed the culture and functioning of the human society as a whole.

5 Physics Physics is thus very much a part of the world around us and is relevant and important for all of us. It has perhaps been rightly said, A basic, and almost fundamental requirement, for an informed and enlightened citizenship of the 21 st century, is to have a basic understanding of the principles by which the physical world operates. As teachers, and more importantly, as students of physics, we all have to constantly put in our intellect, ingenuity, dedication, hard work and perseverance, together to have more and more of citizens meeting the above basic requirement. We now have a vast, complex and exciting picture of the universe----from its atomic to extragalactic range. However the words of Sir Issac Newton, put forward almost three hundred years ago, are very much relevant even now and perhaps forever.

6 Physics Newton is reported to have said I do not know what I may appear to the world but, to myself, I seem to have been like a little boy,playing on the sea shore and diverting myself, now and then, in finding a smoother pebble, or a prettier than ordinary shell, while the great ocean of truth lay all undiscovered before me. The challenge of finding smoother pebbles, prettier shells and exploring undiscovered oceans of truth is still there for all of us. And we need to continue to encourage the STUDENT in all of us to complete as much as possible of this intellectually satisfying and practically useful never ending task.

7 Career Options The study of Physics – apart from providing us with intellectual and philosophical thrill and satisfaction – enables the individual to choose from a vast variety of useful and rewarding careers. A graduate, or a post graduate in Physics can join any one of the fields of engineering, Industry, Astronomy, Information Technology, Robotics, Economics, Software development and programming, research, education, space travel, medical physics and so on. Physics not only has a lot of interfacing, interaction and overlapping with other sciences but also promotes process skills and problem solving abilities in the learners. These features, along with its vast industrial and technological applications should make every student and learner of Physics to feel good and fortunate in having had a chance to study and understand this fundamental, beautiful and fascinating subject (With inputs from the Internet and FACETS OF PHYSICS (A Conceptual approach) – by Roger B. Culver. Acknowledged with grateful thanks.)

8 Typology of questions in 2014 S.NoTypologyWeightage in Marks Weightage in Percentage 1Knowledge based1420 2Conceptual understanding2130 3Inferential type1420 4Reasoning based1115 5Skill based1015 Total70100

9 Typology of Questions in 2015



12 Conceptual Clarity – Points To Be Highlighted Coulombs law – The direction of the force on charge 2 due to charge 1 is along the position vector ( ) of charge 2 w.r.t. charge 1. Calculation of the relevant unit vector; permittivity. Quantized nature of charge significant only at the microscopic level; Quark dilemma? Superposition Principle – significant principle : mutual inter action between two charges is unaffected by the presence or otherwise of other charges.

13 Electric Field – defined mathematically, can be associated with a physical meaning and provides an elegant way of understanding the electrical characteristics of a system of charges. Accelerated charges produce e.m. waves/electro magnetic fields which are regarded as physical quantities : speed of propagation of e.m. waves = c Electrical field line – an institutive non mathematical way of visualizing electric field; properties are associated with them. Electrical Flux - concept carried over from hydrodynamics; associated with rate of flow. Flux is non-zero through a closed surface only if it contains a source or a sink.

14 Electric Dipole – A very useful entity for understanding behavior of matter at molecular/atomic level. Field varies as ; faster than that of a point charge. A dipole experiences only a torque in a uniform external electrical field ; however, there is both a torque and a force in a (highly) non-uniform field. Gausss law : An alternative way of stating Coulombs law. A consequence of the inverse square nature of Coulombs law; we can have a Gausss law for other inverse square fields also. We use Gausss law to calculate electric field, form electrical flux. Hence its application gets limited to special, symmetric charge distributions.

15 Electrical Potential : A useful scalar quantity for describing / mapping an electric field. Not defined uniquely; choice of zero is arbitrary. Can be viewed as a measure of the P. E. per unit charge. Relation between potential and electrical field need to be viewed carefully. Component of electrical field, in any direction, equals the negative of the rate of change of potential in that direction. Comparison of the variation of potential (as ) with that of the electric field (as ). P.E. of a system of charges equal the work done in assembling the configuration and would depend upon whether, or not, an external electrical field is also present.

16 Question No.1 : A (source) charge, Q, and a (test) charge, q, are located at the points (2, 3) and (4, 5) respectively. Keeping charge Q fixed in its position, the charge q is moved to the point (0, 1). How does the magnitude and direction of the force, experienced by q, change due to this shift in its position?


18 Question No.2 : A parallel plate capacitor has the space between its plates filled with a dielectric. Whose dielectric constant varies with distance (from the negative plate) as per the relation? K(r)= K o + α r Show that the capacitance, C, of the capacitor, is given by


20 Question No.3 : A charged solid sphere of radius R has a radial charge density. ρ(r) = k r Draw graphs showing the variation of the electric field due to this sphere, with the distance r, of the field point from its centre. At what point does the field have its maximum value? Where does the field become zero?



23 Question No.4: The x- component of the electric field, of a charge distribution varies with distance, along the x-axis in the manner shown. (a) What is the potential differences between the points x = 2m and x = 10m? (b) Find the change of potential energy of a charge of 10 C as it is moved from x = 4m to x = 8m.


25 Question No.5: (on Dielectrics and Capacitors) A dielectric, of dielectric constant K, is introduced between the plates of a capacitor so that it fills 3/4 th of the separation between them. If a similarly modifier originally similar capacitor is now just is parallel with it, the capacitance of this combination becomes n times that of either of the original unmodified capacitors. Obtain an expression for K in terms of n.


27 Current Electricity

28 Conceptual Clarity – Points To Be Highlighted Definition of Electric current Concepts of drift velocity and random thermal velocity. Mobility equals drift velocity / charge. The establishment of current in a conductor is caused by local electron drifts resulting form an almost instantaneous establishment of electric field in the conductor. Current density vector and its significance Understanding Ohms law – concept of relaxation time.

29 Understanding the difference in the resistivity change behavior of conductors and semi conductors. Electrical Energy & Power; how does transmission at high voltages help in reducing transmission power losses. Special properties of resistor combinations in series and in parallel. Cells; their combinations in series & parallel; internal resistance ; difference between terminal p.d and emf. For the parallel combination : Physical significance of Kirchoffs rules; their use in practical situations and adoption of an appropriate sign convention.

30 Wheat stone Bridge; meter bridge; relevant problems. For a balanced Wheat stone bridge there is no current in the detector arm. Principle of a Potentiometer; two simple practical applications. Two causes for one sided deflection in a potentiometer and understanding the practical difference in the two cases. Using potentiometer (along with Ohms law) to measure currents and resistances. Increasing the sensitivity of a potentiometer.













43 Magnetic effects of Current and Magnetism

44 Conceptual Clarity – Points To Be Highlighted Basic source of magnetic field – moving charges or currents. Charges – static or moving – always produce an Electric field. However, it is only moving charges that, in addition, also produce a magnetic field. Charges – static or moving – always experience a force in an external electric field. However, it is only moving charges, that, experience a magnetic force, i.e. a force due to a magnetic field. Magnetic force in given by the expression Its direction can be worked out by using the standard coordinate axis system and the well known relations for the cross products amongst the unit vectors

45 We can use the above force expression to define (i) the direction of the magnetic field at a point and (ii) the unit of the magnetic field. Magnetic force on a current carrying conductor.. General helical nature of the motion of a charged particle in a magnetic field; radius of helix = ; pitch of helix. Time period / frequency are both independent of the velocity / energy as well as the radius. Concept of cyclotron frequency ; principle of a cyclotron. Understanding how an electron field can be used to cancel the force on a moving charge due to a magnetic field and how this idea can be used to design a velocity selector.

46 Amperes Circuital law; realizing it as an alternative form of the Biot-Sarvart law. Its similarity with Gausss law in Electrostatics. Understanding the reasons for the limited possible use of Amperes circuital law. Understanding the significance of the term Enclosed current. Solenoid and Toroid ; Using Amperes law for both. Uniform nature of the near-axis, near centre field of a long thin solenoid. Understanding the similarity in the expressions for the magnetic fields of a long solenoid and a toroid.

47 Combining the results for the (i) magnetic field due to a long straight current carrying wire and (ii) force experienced by a current carrying wire in a magnetic field. Force between two long parallel current carrying wires. Understanding clearly why like currents attract and unlike currents repel. Arriving at the definition of ampere. Torque on a current loop in a magnetic field; it use in the design of a moving coil galvanometer. Basic design and construction of the moving coil galvanometer ; significance of having a radial field in it. Ammeter and Voltmeter; Understanding why the resistance of an ideal ammeter should be zero while that of an ideal voltmeter should be infinite.

48 Errors introduced by finite values of ammeter / voltmeter resistances. How to convert a given moving coil galvanometer into an ammeter or voltmeter of desired range? Equivalence of a current loop to a magnetic dipole – using the analogy with an electric dipoles electric filed. Associating an equivalent orbital magnetic moment with an electron orbiting around the nucleus. Understanding the difference between the current sensitivity and voltage sensitivity of a moving coil galvanometer.

49 Writing expressions for the axial and equatorial fields of a magnetic dipole – from the corresponding expression for the electric field of an electric dipole. at a point in the plane of the loop, at a distance x from the centre(x >> R, the radius of loop) equal nearly. Any planar current loop, of area A, is equivalent to a magnetic dipole of magnetic moment. Looking at the possible applications of this result.

50 Magnetism Magnetism was initially studied as a subject in its own right. It was only in the early part of the 19 th century that Oersted, Ampere, Biot and Savart correlated it with moving charges or currents. The bar magnet, is in many ways, considered similar to an electric dipole. Results for a bar magnet are not derived; they are simply arrived at by comparison and co-relation with an electric dipole. Magnetic field lines help us to have a visual and intitutive picture of a given magnetic field. The closed curve nature of magnetic field lines is a significant difference from the start from positive charge and end at a negative charge; nature of electric filed lines.












62 Electromagnetic Induction


























88 Optics
























112 Dual Nature of Matter






















134 Atoms and Nuclei

135 Atoms How did the concept of a structure of the atom evolve? Discover of electron as a common constituent of all elements. Overall neutrality of the atom as a whole : Hence elements must contain a positive charge also. Basic requirements from a model of the atom: – Electrical neutrality – Stability – Characteristic spectra of elements – line spectra

136 Atoms Suggestion : First by J J. Thomson in 1898 – The Plum Pudding Model Rutherfords suggestions on studying the scattering of alpha particle by atoms to investigate the atomic structure Geiger and Marsdenes experiment in 1911 – The importance of the observed back scattering Rutherfords nuclear model – the entire positive charge and most of its mass is concentrated in the nucleus with the electrons some distance away. Experimental suggestion – nuclear size ~ m to m

137 Atoms Significance of the distance of closest approach – estimate of nuclear size but not quite. Electron orbits – only one condition to determine v and r. Hence a wide range of continuous choice for v and r. Two major drawbacks of Rutherfords model: – Conflict with em theory, no proper explanation of atomic spectra details – Very short lived stability Balmers mathematical studies of the observed spectrum data of hydrogen.

138 Nuclei The unit for atomic masses is 1/12 th of the mass of one carbon 12 atom = 1 u = * 10^ -27 kg (it is useful to remember that 1 u = Mev) Proton – Electron model of the nucleus was not compatible with experimental facts / theoretical concepts Discovery of the neutron in 1932 by James Chadwick through study of the effects of bombardment of alpha particles on berylium nuclei.

139 Nuclei The proton neutron model of the nucleus. Isotopes, Isobars, Isotone Nuclear size (R) are proportional to the cube root to the mass number (A). Hence the largest nucleus would be nearly six times the size of the smallest nucleus. Nuclear density is nearly constant (has very high value) for all nuclei. Neutron stars have comparable density values.

140 Nuclei Concept of nuclear binding energy. An increase in B.E/nucleon implies release of energy and vice versa. Characteristics of nuclear force: charge indefinite and short ranged nature. Must change from a attractive to repulsive if the distance between two nucleons decreases below a certain value (~0.8 fm) No simple mathematical formula now understood in terms of QUARK picture of the nucleon.

141 Radioactivity Why was radioactivity regarded as a nuclear property? Radioactivity is the spontaneous continuous decay of some unstable nuclei. Exponential nature of the law of radioactive decay. Decay rate R (= -dN/dt), is linked with the activity of the sample. Decay rate is measured in the units of becqurel (Bq). 1 Bq equals 1 decay per second.

142 Radioactivity Concept of half life and mean life and their correlation with the decay constant [half life = (0.6931) mean life = /decay constant] Useful tip for solving radioactive decay problems – To find number of atoms left over in time t, calculate p (= t/T, T= half life). The number left over is two to the power minus p of the original number. For calculating the time t in which n out of N atoms are left over, calculate p through the equation 2^ -p = n/N. t then equals p times T where T= half life

143 Radioactivity Essential details of alpha, beta and gamma decay – change of mass number, atomic number and release of energy. Understanding beta decay through inter conversion of proton and neutron, Necessity of neutrino. Production of nuclear energy through nuclear fission and fusion. Q value of a nuclear reaction equals (average final B.E / nucleon – average initial B.E/ nucleon) * initial total number of nucleons. Nuclear reactor and fusion reactions in stars.


145 Examples Question No.1: A nucleus of mass number200 initially at rest emits an α-particle. The Q-factor of reaction is 5 MeV. What is the kinetic energy of emitted α-particle? Let m α and m n denote mass of α-particle emitted and the daughter nucleus. Let v α and v n be the speed of the two. From law of conservation of linear momentum m α v α + m n v n = 0 or v n = - (m α /m n ) v α (1) From law of conservation of energy

146 Examples m α v α 2 + m n v n 2 = 5. 0 MeV Or m α v α 2 + m n [ (m α /m n ) v α ] 2 = 5.0 Or m α v α 2 [ 1 + (m α /m n ) ] = 5.0 Kα = K.E of emitted α- particle = m α v α 2 Also m α =4; m n = 200-4=196 Therefore Kα [1 + (4/196)] = 5.0 Or Kα = 5 x 196 /200 MeV = 4.9 MeV

147 Examples Question No.2: Hydrogen atom in ground state is bombarded with a particle having energy (a) 8.0 eV (b) 11.0 eV. In each case how much energy is transferred to the hydrogen atom? Is collision elastic or inelastic? The allowed energy states of hydrogen atom are En = - eV E 1 = eV, E 2 = -3.4 eV, E 3 = – 1.51 eV,……. =0

148 Examples Case (a) Since hydrogen atom is in its ground state its energy is eV. The total energy of hydrogen atom it gains the complete energy of incident particle will be ( ) eV = -5.6 eV. There is no allowed energy state corresponding to this value. The electron in hydrogen atom has no allowed energy state if it absorbs a part or whole of the energy of the incident particle. Therefore it accepts no energy from the incident particle. Therefore it accepts no energy from the incident particle. In other words energy transferred to hydrogen atom is zero. The total K.E. of hydrogen atom and incident particle is conserved, therefore collision is Perfectly elastic.

149 Examples Case (b) The energy of incident particle is 11.0eV. The hydrogen atom absorbs 10.2eV of energy and goes to the first excited state. The energy of incident particle after collision is =0.8eV. The total K.E. is not conserved in this collision. The collision, therefore, is inelastic.

150 Examples Question No.3:A hydrogen atom in its first excited state returns to ground state by emitting radiations of wave length λ 1. The wave length of emitted radiations is λ 2 if it returns from 2 nd excited state to 1 st excited state. What is the wave length of radiations emitted if it returns from 2 nd excited state to ground state in one go? From Bohrs second postulate En 1 - En 2 = hν = hc/ λ The first excited state corresponds to n = 2 For ground state n = 1.Therefore E 2 – E 1 = hc / λ (i)

151 Examples For second excited state corresponds to n = 3. Therefore E 3 – E 2 = hc / λ (ii) For ground state n = 1. Therefore Let λ be the wave length of emitted radiations when electron jumps from second excited state (i.e.n = 3), to the ground state (i.e. n=1).Then E 3 – E 1 = hc / λ (iii) From eq. (i), (ii) and (iii)

152 Examples Question No.4: The allowed energy states of some hypothetical atom is given by En = - eV Where k is a positive constant. In this atom photon of energy 2 eV is emitted when electron jumps from first excited state to ground state. What is energy of photon emitted due to transition from second excited state to ground state? This photon is incident on a photo sensitive material having work function of 1.07 eV.What is stopping potential of emitted photoelectron? The transition from first excited state to ground state corresponds to n 1 = 2 to n 2 = 1.

153 Examples


155 When this photon of energy 2.37eV is incident on photo-sensitive surface; the maximum K.E of emitted photoelectron is K max = hν – w min = =1.3 eV. Let Vs be the stopping potential of the emitted photoelectron; then K max = eV s. Hence V s = 1.3 V.

156 Examples Question No.5: A nucleus of 236 Ra 88 decays to 222 Rn 86 by the emission of an α-particle of energy 4.8MeV. What is recoil energy of radon? Let m; m 1 and m 2 denote mass of radium, radon and α- particles respectively. Before emission the radium nucleus is at rest. Let v 1 and v 2 be the speed of radon and α - particle after emission. From law of conservation of linear momentum 0 = m 1 v 1 + m 2 v 2

157 Examples


159 Question No.6: An electron is contained in a hollow tube. The electrons potential energy in one half of tube is zero, while in the other half it is l0 eV. The total energy of electron in tube is 15eV. What is the ratio of the de Broglie wave length of the electron in the two halves of the tube? The de Broglie wave length λ, of electron is

160 Examples

161 Question No.7: In hydrogen like atom 47.2 eV of energy is required to excite electron from first excited state to the next higher energy state. What is Z of the atom? What is kinetic energy, potential energy and the angular momentum of the electron in the first permitted orbit? The energy E n ; in n th allowed orbit of a hydrogen like atom having atomic number Z is

162 Examples The first excited state of atom corresponds to n 1 = 2. The next energy state corresponds to n 2 = 3. Given

163 Examples




167 From Bohrs quantization condition mv n r n = nh/2π (iii)

168 Examples




172 Question No.11: A photon of energy 10.2 eV collides inelastically with a hydrogen atom in ground state. After a few microseconds another photon of energy 16.oeV collides inelastically with the same hydrogen atom. What is recorded in a suitably placed detector? The different allowed energy states of a hydrogen atom are

173 Examples Therefore E 1 = eV, E 2 =- 3.4 eV, E 3 = eV, When a photon of energy 10.2eV collides inelastically with hydrogen atom in ground state; the photon is absorbed. The hydrogen atom goes to first excited state. The second photon collides with hydrogen atom after few microseconds. In the mean time the excited hydrogen atom returns to its ground state emitting a photon of 10.2eV. The energy of second photon (= 16.0 eV) is more than the ionization energy of hydrogen atom in the ground state. This photon causes ionization of hydrogen atom and the emitted electrons has a kinetic energy of 16 – 13.6 = 2.4eV. The detector, therefore, detects a photon of energy 10.2eV and an electron having a kinetic energy of 2.4eV.

174 Electronic Devices

175 Pure semiconductors (intrinsic) and controlled impure semiconductors (extrinsic) Remember: A bulk sample of either an n-type of a p-type semiconductor is electrically neutral. n e n h = n i 2 Forbidden energy gaps for carbon, silicon and germanium are 5.4 ev, 1.1ev, 0.7ev respectively. It is 0.0ev for tin. Hence the difference in their behaviors. Formation of pn junction. It is not a joining of a p- type slab with a n-type slab.

176 Electronic Devices Formation of depletion layer or region. This is a region devoid of free charges but is a space charge region (immobile negative charge region on the p-side and positive charge region on the n-side) Space charge regions cause the development of a Barrier Potential Even very small potential differences, across the junction, can cause very strong electric fields over the depletion layer because the thickness of this layer is of the order of m. P-N junction diode: Important – effective barrier height (under a forward/reverse bias V) equals original barrier height minus/plus V.

177 Electronic Devices The reverse current, due to the minority charge carriers, can increase considerably if the reverse bias exceeds its characteristic critical value. Concepts of threshold voltage and Reverse Saturation currents for a diode. Breakdown of a diode under reverse bias. Rectifying Action: Half wave + Full wave rectifiers Special Purpose Diodes – Zener Diode – Much heavier doping – Breakdown – Due to internal field emission – Difference - between Avalanche + Zener Breakdown

178 Electronic Devices Optoelectronic junction devices – carriers are generated by photons Three types : Photodiodes (for detecting optical signals) LEDs (for getting light from electricity) and Photovoltaic cells or solar cells (for getting electricity from optical radiation) Minimum energy of photons needed in a photodiode should exceed its band gap. Reverse biasing is preferred. LEDs are heavily used p-n junction diodes which, under forward bias, emit radiation spontaneously. Visible light semiconductors have a band gap of at least 1.8ev.

179 Electronic Devices Solar cells – no external bias applied and the junction area is kept much larger than in a photodiode. Requirements – band gap (1.0 to 1.8 ev), high optical absorption, good electrical conductivity, availability, cost. Transistor – symbols and types Two differences between emitter and collector – doping and contact size. Active state of the transistor – Emitter-base action acts as a low resistance while the base collector acts as a high resistance.

180 Electronic Devices Circuit for transistor characteristics and shape of these characteristics. AC parameters of a transistor – input resistance (~ a few hundred to a few k ) output resistance (~ 100 k )and current amplification factor (β) (= I c / I B ). We also define (β dc ) (= I c / I B ). Three regions in the transfer characterstics: cut off region (Vi, threshold voltage), active region, saturation state.

181 Electronic Devices Amplifier action : V o = V cc – I c R c, V i = I B R B + V BE V o / V i = - R c/ R B ( I c / I B ) = - β ac (R c/ R B ) Feedback + Oscillator action Analog + Digital signals Basis of Logic Gates: (basic circuits that process the signal in a specific manner) NOT gate, OR gate, AND gate, NAND gate, NOR gate, combination of gates.

182 Communication Systems

183 Basic elements – Transmitter, channel (medium), Receiver Basic Terminology – Transducer, Signal, Noise, Transmitter, Receiver, Attenuation, Amplification, Range, Bandwidth, Modulation, Demodulation, Repeater Bandwidth of signals –why is it there? Bandwidth of transmission medium Different methods of propagation of em waves

184 Communication Systems Ground waves or surface waves – wave glides over the surface of the earth and is constantly attenuated Sky waves – involve ionospheric reflections have a upper limit (~30 MHz) Direct straight line travel from transmitting antenna to the receiving antenna. Line of sight communication. Maximum Range = 2Rh T + 2Rh R

185 Communication Systems Television Broadcast, Microwave links, Satellite communication are all examples of space wave mode of propagation. Modulation – its meaning and necessity Three important reasons: size of the antennae, effective power radiated, and Mixing up of signals. Amplitude Modulation and Modulation Index. Production and Detection of AM waves. Recent amazing advances in Communication systems.

186 Value based Education


188 Live,so that when your children think of fairness and integrity, they think of you. H. Jackson Brown Do not erase the design the child makes in the soft wax of his inner life. Maria Montessori

189 Need for strengthening a system of value oriented education Ancient education had a code of ethical conduct and education of the pupil was centered around such a code. But,over the years, the educational system, for one reason or another, has lost sight of its value culture. Recent thinking has led to the realization that we need to ensure quality along with aquantitative expansion of education.

190 Continued… It needs to be realized that we can have a just, systematic and orderly society only when VALUES are made an inseparable part of human being. There is,therefore, an urgent need for strengthening a system of value oriented education and the recent step, of CBSE, of making Value Based Questions a part of the question papers, of all subjects, is a meaningful step in that direction.

191 DEFINITION OF VALUE Several definitions of the term Value : A broad tendency to prefer certain states of affairs over others. A value is a belief upon which humans act by performance. Values are ideals, beliefs, morals or spiritual principles which need to be an important and integral part of our living.

192 Continued … There are certain values which have been generally accepted and followed, all over and which can, therefore, be viewed, as approaching a universal and absolute nature. We generally think of mainly these values when we lay emphasis on VALUE EDUCATION.



195 DEFINITIONS OF SOME STANDARD VALUE TERMS FORGIVENESS : Ceasing to have bad feelings against another for what they may have done to you. COMPASSION:Feeling sorrow or pity for others in difficulties. ENTHUSIASTIC:Having a strong and eager interest in a particular area.

196 Continued… STEADFASTNESS: Being firm in purpose, faith and loyalty. INTEGRITY : Being honest and following your principles. THANKFULNESS:Being able to express feelings of gratitude through words or actions.

197 Continued… PATIENCE: Being calm when waiting. GENEROSITY:Unselfish and always ready to give and to share with others. TRUTHFULNESS:Being genuine and honest in all things you say.

198 Continued… THOUGHTFULNESS: Being,at all times, considerate and kind to others. FLEXIBILITY: Having the ability to change or adapt to new things. CREATIVITY: The ability to think and create in an original way.




202 CONCLUSION In short, value based education helps A child to evolve into a complete human being and not just a social or biological entity. The society as a whole, but parents and teachers, in particular, play a pivotal role in understanding of values of in a student and helping him/her to develop all dimensions of his/her personality and evolve into a perfect human being.

203 CONCLUSION One can say, A VALUE HAS A VALUE ONLY IF ITS VALUE IS VALUED. The need of the hour, therefore, is to: REVIVE and REINFORCE the spirit of human values and to restore faith in the eternal truths.


205 Loud Thinking : Some suggestions For Value Based Questions Physics Concept Unit 1: i) Need for units. ii) Dimensions. Suggested Situation/ Link i) Can be linked with time management. ii) Can be linked with the dimensions and values needed in life.

206 Physics Concept Unit 2 i) Different types of motions take place different circumstances or forces on a system but the basic relations between displacement, velocity and acceleration always remain intact. Suggested Situation/ Link i) We need different kinds of behavior and values in different circumstances but we need to ensure that our basic or core values always remains intact.

207 Continued… ii) Projectile motion Same range achieved through different paths but with changes in the trajectory, time of Flight and maximum height. Maximum range achieved when the angle of projection is 45°. ii) We can achieve our goals through different approaches. The satisfaction and appreciation achieved, however, is maximum when we stick to basic core values.

208 Physics Concept Unit 3 i)Inertia: ii) Definition and need of and external force for bringing about a change in state of motion. iii) Impulse : Change in momentum. Suggested Situation/ Link i) Tendency of making Inertia a usual part of our life; its likely positive and negative impacts. ii) Impact of external causes (value based) on our life.

209 CONTINUED… iv) Conservative and non conservative forces v) definition of momentum. vi) Conservative laws : iii) Correlation with a Positive( sudden ) thought and change caused by it. iv) Positive and negative values v) Effect of one (mass) or other (velocity relates) change on the momentum of our life. vi) Need for conservation of values

210 Suggested Situation/ Link i) Correlation with some appropriate life situation. ii) Conservation of values based on systems and their impacts on society. Physics Concept Unit 4 i) Definition of work. ii) Work energy theorem Law of conservation of energy.

211 Continued… iii) Need for minimum initial velocity for looping the loop. iv) One dimensional elastic collision v) Inelastic collision. iii) Need for hard work and dedicated nature for success in life and achieving goals. iv) Correlating situation corresponding to m 1 = m 2, m1>>m 2, m 1 <

212 Continued… vi) Two dimensional collisions. vii) Coefficient of restitution. vi) Correlating with the need for having some prior information for a complete evaluation of a system. vii) Correlating with the extent of determination, steadfastness displayed in challenging situations.

213 Physics Concept Unit 5 i) Centre of mass. ii) Shift in the centre of mass. Suggested Situation/ Link i) For identifying the central or the most important point in the given problem. ii) Need for shifting our goal or aim as per the situation.

214 Continued… iii) Advantage of concepts of rotational motion. iv) Torque can be large for a small force iii) Do in Rome as Romans do, situation. iv) Small consistent and dedicated effort can yield quite significant results.

215 Continued … v) Moment of inertia can be changed even when mass does not change (through change in axis of rotation). vi) Radius of gyration/ Centre of mass. v) The same person can do different things by adjusting his/her way of working. vi) Concentration of output/effort-positive or negative.

216 Continued… vii) Rotational motion - Rolling motion - Slipping-role of normal reaction.. vii) Rolling stone gathers no moss. Bonding of individual through sharing of ideas and efforts.

217 Physics Concept Unit 6 i) Universal nature of the law of gravitation ii) Independence of g from mass. Suggested Situation/ Link i) Universal nature and effect of basic values at different places and times. ii) Non personal nature of values.

218 Continued… iii) Similar nature of variation of g with height and depth. iv) Satellite motion. iii) Show of similar resilence in different situations. Decrease of lack of determination with increase or decrease of facilities/infrastructure. iv)Effect of bonding/ love/ considerate behaviour.

219 Continued… v) Escape velocity its different values for different planets. vi) Moon cannot hold onto the atmosphere. v) Minimum effort to come out of negative situation, its variation with the variation of situation. vi) Lack of concentration and regularity makes it difficult to hold on to learnt concepts and values.

220 Physics Concept Unit 7 i) Perfect gas / no intermolecular Interaction. ii) Ideal gas law(tends to be obeyed at high temperature and lower densities. Suggested Situation/ Link i) Perfect behavior and dedication/ no effect of ordinary distractions. ii) Aim to achieving our own set of ideals through higher degree of effort, determination and dedication.

221 Continued… iii) Change of phase critical temperature and pressure (liquefaction of gas requires the Temperature to be made lower than the critical temperature). iii) Mere doing of work or effort without a critical and clear analysis of the goal to be achieved is not likely to achieve any tangible result or a change of phase vis - a - vis our present situation.

222 Physics Concept Unit 8 i) Elasticity + plasticity. Suggested Situation/ Link i)Both needed in life we should tend to be elastic for upholding universally accepted value and plastic for accepting better ideas, innovation and requirement consistent with changing times..

223 Continued… ii) Stress + strain. iii) Hooks law; its breakdown. ii) Strain is the cause of stress and stress develops in trying to undo the effects of strain. iii) More the strain, more is the stress in life; there usually is a breakdown point for all of us.

224 Continued… iv) Different material have different levels of malleability, ductility and brittleness. v) Poissons ratio iv) Visualization and framing of situation to similar difference in human nature and behavior. v) Visualizing how one kind of strain can lead to a proportional increase in another type of strain in some other dimension.

225 Continued… vi) Elastic fatigue vii). Viscosity/ existence of internal friction during flow of fluids. vi) How monotony can lead to mental fatigue and retention of irrelevant ideas and results. vii) Situation depicting internal friction or difference vis- a- vis. flow or execution of some project or work.

226 Continued… vi) Terminal velocity its importance and uses. vii) Stream lined flow. vi) Situation where one tries to make the best use of the situation even after reaching the end of the Road. vii) How nature and man made machine benefits through stream lined rather than turbulent behavior.

227 Continued… vi) Reynolds number. vii) Bernoulli's theorem. ( increase of pressure leads to decrease in velocity and vice versa). vi) How a combination of Factors, beyond some critical limit, can lead to a breakup of the stream lined flow of ones life. vii) Combination of two Factors, where an increase of one leads to a decrease of other, and vice - versa.

228 Continued… vi) Practical application of Bernoulli's theorem. vii) Surface tension ( difference between behavior of surface molecules and molecules in the deep). vi) Situation where ones can use a decease of one factor or facility to bring a increase in the other. vii) Situation where in the difference between the framed or outward and the real intention or behavior is brought out also- Aad Jal Ghagri Chalkat Jae.

229 Continued… vi) Cohesive and adhesive forces. vii) Excess pressure inside a drop is double that in bubble. vi) Bonding of family and friends and bonding with strangers. How situations can change the relative magnitude of two. vii) A person filled with universal accepted values may be twice useful than one who has these only on the surface or just for an external or pretended show.

230 Continued… viii) Rise in a capillary tube compared to that a wide mouthed tube. ix) Effect of temperature changes or causes like addition of detergent on surface tension( viscosity). viii) Relative small infrastructure having relative fewer facilities – may achieve higher goals than one with an excess of these. ix) Effect on our behavior, or Output, of factors like change of situation infrastructure or facilities on our nature, behavior, determination and dedication.

231 Continued… x) Thermal expansion: - Making use of it - Its effect and precaution needed. xi) Specific heat capacity and latent heat capacity. x) Expansion of facilities - Infrastructure etc. -Their uses,their effect and care needed in different situations. xi) Making use of specific skills; looking for latent skill and using them for change of state.

232 Continued… xii)Different methods of conduction of heat. xiii) Thermos flask. xii) Making use of, and changing the technique, as per requirement For enhancing, and improving the output. xiii) Situational setups that can insulate a System, or a setup, from disturbance or negative factors.

233 Physics Concept Unit 9 i) Atomic / molecular nature of matter microscopic events or happening control macroscopic behavior. Suggested Situation/ Link i) It is the small, or grass root workers, whose output goes to control the performance of a large organization or factory..

234 Continued… ii) Impact of molecules on the wall produces pressure and gas laws. iii) Avogadros number: Same value for 1 gram mole – irrespective of nature of gas. ii) Impact of positive thoughts / efforts on the otherwise rigid society can produce sufficient pressure to change society for the better. iii) Universally accepted values – always the same – irrespective of nature, location or structure of society.

235 Continued… iv) First law of thermodynamics- another way of stating the law of conservation of energy. v) Second law of thermodynamics- a natural built constraint and vis – a-vis direction of heat flow. iv) Example of different situation/ behavior where same values hold. v) Situation illustrating how good values/ thoughts/ knowledge flow from a person at a higher level of these – irrespective of material,monetary or infrastructure facilities.

236 Continued… vi) Mean free path. vii) Nature of different types of changes- isothermal, adiabatic, isobaric, isotonic and their characteristics. vi) Randomness of happening or events but on the whole, there is mean or average result or output. vii) How maintaining constancy, of one parameter can lead to a change in the nature of the interaction between two other parameters.

237 Physics Concept Unit 10 i) Periodic and non periodic motions. ii) S.H.M – how it builds Up all other types of periodic motions. Suggested Situation/ Link i) Regularity and irregularity vis - a -vis observance of values. ii) How one or other basic value can lead to a buildup of other values.

238 Continued… iii) Phase Relationships. iv) Waves – can transfer energy. iii) Situations illustrating phase relationships between behavior and values. iv). Values can be made to get transfered without bringing in any materialistic transfers..

239 Continued… v) Difference between longitudinal and transverse wave. vi) Development of equation of S.H. wave. v) Difference between direct or indirect ways of transfer of values. vi) Impact and correlation of present and past situation or achievements..

240 Continued… vii) Super position of waves- Principle of super position. viii) Interference/ need for coherence. vii) A very important message- like the waves our content of values should be unaffected by the presence or absence of other values,or Situations, or circumstances. viii) Situation where a coherent interaction can lead to maxima of positive thoughts and minima of negative thoughts/ values.

241 Continued… ix) Beats. x) Doppler's effect: Effect of relative motion / its dependence on direction, nature and cause of relative motion. ix) Superposition of slight changes and adjustments can increase / improve the sweetness / impact of our joint efforts. x) Effect of relative adjustments and changes and dependence of the out put on the direction, nature and cause of relative Adjustment/changes.

242 Electrostatics

243 Current Electricity

244 Magnetic effects of Current & magnetism Magnetic field is associated only with moving charges or currents ( An idea/concept,when put in action/motion can bring in additional results) Oersteds experiments / Biot Savart rule ( A (mis)directed action may produce results in a different direction) Amperes Law ; an alternative way of stating Biot Savart rule (Suitable change/modification can lead to a simplification of the problem) Infinite wire --concept based on a relative comparison of two sizes (All our interpretations/experiences of our situations are basically relative in nature. Even a small achievement can lead to what may appear as infinite joy.) Solenoid --itself a curved entity, produces straight parallel lines of magnetic field near its axis. (There can be situations where an apparently complicated input can lead to a surprisingly good straight result) Cyclotron –a clever use of the shielding effects of conductors, and the ability of a magnetic field to make charged particles move along circular pathsenable large accelerations to be achieved over relatively small sized apparatus. (An intelligent use of the diverse skills/abilities of two devices/persons can enable one to get surprisingly good and enlarged results/outputs.) Force between two long parallel current carrying wires: Like currents attract each other while unlike currents repel each other. (Two persons, with similar thinking/approach towards problems/tasks can cooperate to give attractive/enhanced results.) 8. Moving coil galvanometer ---addition of suitable resistors can push up its range as an ammeter or as a voltmeter. (Suitable additions/additional devices/sharing of positive thoughts or actions, can push up the output/performance of a machine/device/person.) 9.Para, Dia and Ferromagnetic substances.-----show different types of interactions with an external magnetic field. (There may be only a slight or casual positive effect or a negative effect or a strong positive effect when different persons interact with positive thoughts/ concrete and decisive actions) 10. Electromagnets are temporary and adjustable magnets which can be easily switched ON or OFF. Permanents magnets, on the other hand, have a constant permanent magnetism which stays ON for a long time. ( There may be only a temporary show of (adjustable) loyalty/dedication/honesty/sincerity vis-à-vis an organization/person as contrasted with a definite and constant display of such qualities.)

245 Electromagnetic Induction and Alternating Currents A magnet, in relative motion, can induce a current in a coil. (Good actions / observance of values can induce respect for,or acceptance of VALUES.) Eddy currents, generally a cause of wastage of energy, can be put to useful USE through suitable adjustments. ( One can make suitable adjustments to draw positive outcomes from apparently negative situations.) An alternating current, in spite of changes in its magnitude and direction, always keeps on producing heat in a resistor. ( A dedicated/ determined person always keeps on advancing towards her/his goal in spite of the difficulties /deviations that she/ he may encounter.) The current, in an A.C. circuit, is, in general, not in phase with the applied E.M.F. (Casual and careless efforts, in general, do not produce an output in sync with the input.) In an LC circuit, the phase lag produced by the inductance, can be balanced by the phase lead provided by a capacitor of appropriate value. ( The negative effects,of a disruptive action, can be balanced by an appropriate positive action.) The LC, and the LCR,circuit can show RESONANCE at a particular frequency of the applied E.M.F. (By making the external environment in tune with a childs natural preferences, the child learning can show a resonance like effect.) Wattless currents---- The inductor,or the capacitor, on the average, draw zero power from the source. They give back as much to the source as they withdraw from it in successive quarter cycles. (Human beings can enrich the society, and the human race as a whole, by giving back at least as much as they withdraw from it.) AC generator --- transforms different forms of energy into electrical energy. (We should aim to make ourselves into educated, cultured and humane Human beings by taking different types of INPUTS from different sources.) Transformer--- can step up or step down an AC voltage but cannot do so for a DC voltage. (Good company /good advice helps to step up our good qualities whereas bad company/ bad advice does just the reverse.) Power factor -- increases with an increase in the resistance of the circuit. (Our will power can show an increase with an increase in our determination.)

246 Electromagnetic Waves 1.Inspite of the differences in their frequency/wavelength, all e.m. waves propagate with the same speed in vacuum. (inspite of the differences in their caste, colour or creed, the basic VALUES for all human being s are the same.) 2. EM waves, of different frequencies/ wavelengths have quite marked differences in their properties and uses. (we need to accept, acknowledge and appreciate the differences in the culture and characteristics of human beings of different cultures and socities.)

247 Two new initiatives Problem Solving Assessment (PSA) PSA is a measure that aims to create an enjoyable learning environment and stimulate curiosity and creativity. It has been designed in a way that would help to improve the generic and higher order thinking skills. It aims at assessing a students creative and critical thinking, decision making, and problem solving and communication skills. For this purpose, it makes use of unorthodox questions which are not subject specific. It is hoped that this initiative would greatly assist learners in toning up their skills in research and analysis, ability to apply different concepts of subjects, solve application based problems in mathematics and science, comprehend and analyze written text and effective communication. All these dimension of 21 st century life skills should help learners to face subsequent challenges of life with an enhanced degree of confidence. Open Book System OBS is indeed an open text based system in which students will be supplied reference material a few months before the examination. They would be expected to make themselves familiar with this material in a complete and holistic way. In the examination, they would be asked questions based on the material supplied. The objective of introducing open text based examination is to provide opportunities to students to apply theoretical concepts to real life scenarios by encouraging active and group learning in the class. Active discussion on case studies, or other material supplied by the board, is expected to train students in effective use of memory and acquiring skills of processing information rather than on rote learning. Learning should thus become an enjoyable activity that is more effective and long lasting. Combined with teaching that focuses on developing thinking skills, open book examination can become an exciting and interesting intellectual adventure.


249 HOTS (Higher Order Thinking Skills) The concept of HOTS introduced by CBSE in its class X and XII examinations, from the year 2008 is a fundamental concept of Education Reform, based on Blooms Taxonomy. This taxonomy lists the following six levels ( in increasing order) in the hierarchy of cognitive processing. Knowledge, comprehension, Application, Analysis, Synthesis and Evaluation.

250 In the words of David.W.Dilliard, we may define HOTS as follows In the words of David.W.Dilliard, we may define HOTS as follows: Higher order thinking skills (HOTS) essentially mean that thinking that takes places in the higher levels of hierarchy of cognitive processing and can be viewed as a continuum of thinking levels starting with knowledge level thinking and moving eventually to evaluation level of thinking. HOTS basically aims at developing and increasing cognitive development or critical thinking. It aims at teaching students reasoning and processes – rather than teaching them simple recalling of facts -and is expected to make them better life long learners. Its aim is not on drill and repetition activities but on Problem Solving and higher order thinking skills. HOTS thus moves away from simple general knowledge type skills to thinking skills like Synthesizing, Analyzing, Reasoning, Comprehending, Application and Evaluation.

251 It is interesting to note that HOTS questions are not necessarily difficult questions. They simply require the ability to relate knowledge from several areas, to use methods, concepts and theories in new situations, to observe regularity and patterns and to organize the parts of a problem into a whole. If done in a systematic,simple and interesting manner, HOTS help in developing better problem –solving abilities and doing critical thinking,analysis and evaluation. It is interesting to note that research has indicated that even students, who are not good at simply memorizing facts and figures, tend to benefit from learning and developing higher order thinking skills that teach them the ways and techniques of solving problems.

252 The learning Research and Development Center (1991) has listed the following as higher order thinking skills: Size up and define a problem that is not neatly packaged. Determine which facts and formulae, stored in memory, might be helpful for solving a problem. Carry out complex analysis or tasks that require planning management monitoring and adjustments. Recognize where more information is needed and where and how to look for it. Step outside the routine and deal with an unexpected breakdown or opportunity.

253 CBSE, from the year 2008, has moved away from simple, knowledge, understanding and application questions to questions that are data based or open ended or based on analysis and interpretation of graphs or drawing graphs based on suitable mathematical results or formulae or data or activity based or require sharp alternative thinking. It is hoped that this new format of question framing will induce and encourage more and more concept based teaching that will make students, better learners and problem – solvers.

254 Suggestions for students The following are some ideas that should assist students in learning. 1. Identify and follow your own style of learning 2. Remember it is necessary as well as important to understand,and develop, good study habits. 3. Ask yourself the following questions: Am I comfortable with the basic concepts of subject learnt by me earlier? Am I comfortable with the basic concepts of mathematics needed for my subject? Am I an active learner? Do I do my studies in a focused way? Can I translate mathematical expression,equations and graphs into word equations and expressions and vice- versa? Do I try to have HANDS -ON experience of my theory concepts in my practical class,whenever and wherever possible? Do I supplement my class room learning by reading other books or by visiting relevant sites on the Internet? Do I regularly try to solve numerical problems to understand,assimilate and apply the theoretical concepts taught to me? Do I attend my classes regularly and listen to the teacher attentively? Do I try my best to have my doubts and queries clarified through discussions with my teacher or my fellow students? Do I set aside adequate and regularly scheduled study time in a distraction free environment? If your answer to any of these questions is a NO,you need to take immediate corrective measures. 4. Remember that you need to go through the whole of the prescribed syllabus, Without skipping or ignoring any topic. 5. The NCERT book defines the DEPTH of coverage of each topic given in the syllabus. 6.It is always a good idea to go through the SUMMARY given at the end of each unit and to have a relook,if needed, at any point,or concept, that does not appear to be clear from the summary. 7. Always maintain a positive outlook and have full faith and confidence in yourself.

255 Suggestions for students The following suggestions should help students to attempt and answer their PHYSICS paper in a more relaxed,comfortable and better way: 1. Relax yourself before reading the question paper. Closing the eyes and 'blanking out' the mind for a few seconds is generally always helpful. 2. Just mentally recite or remember something that gives you a feeling of confidence and relaxation.. 3. Never feel panicky.Read the questions slowly and carefully and just put some cross marks against the questions you don't feel confident about on a first reading. The CBSE gives you 15 minutes time for reading the question paper and digesting the questions. 4. Decide about the alternative you would like to answer in the questions with choice. 5. There is no need to follow any preset sequence in answering the questions.It is always better to first answer the questions you feel more confident and comfortable about. 6. While answering (a) always keep the answer brief and 'to the point'.carefully look at what has been asked in the question and limit your answer to what has been asked. Remember: extra details,not asked for, will not fetch you any extra marks.they will only consume some of your precious time. (b) even if you are not able to/or are in a position to answer/attempt a question in full, never forget to write the answer to whatever part/section/segment of that part of question about which you are confident. (c). Do always write the units of the physical quantity you have calculated in a numerical problem. (d)draw simple, clear and properly labelled out diagrams wherever needed. (e) never forget to write out the names( symbols/units) of the physical quantities used for drawing a graph. (f) always Mark the 'arrows' on a ray diagram and the (+),(-) terminals on the battery/ammeter/voltmeter used in a circuit diagram. (g) never make your answers to different questions overlap each other. Leave clear space/ some lines between the answers to two different questions or to different subparts of the answer to the same question. (h) wherever possible,highlight/underline the keywords/formulae in your answer. (I) always draw a clear line to indicate the 'end point' of your answer to a given question. It is better to answer all the subparts of a question together. (j) a clear, neatly written out answer helps the examiner and thereby the examinee.

256 I AM A TEACHER (John W. Schlatter)

257 I am a TEACHER. I was born the first moment that a question leaped from the mouth of a child. I have been many people in many places.

258 Throughout the course of a day, I have been called upon To be an actor, friend, nurse and doctor, coach, finder of lost articles, money lender, taxi driver, psychologist, a parent, salesman, politician and a keeper of the faith.

259 An architect knows that if he builds with care, his structure may stand for centuries. A teacher knows that if he builds with love and truth, what he builds will last forever.

260 I am a paradox. I speak loudest when I listen the most. My greatest gifts are in what I am willing to appreciatively receive from my students.

261 I am a warrior, daily doing battle against peer pressure, negativity, fear, conformity, prejudice, ignorance and apathy.

262 But I have great allies: Intelligence, Curiosity, Parental Support, Individuality, Creativity Faith, Love and Laughter all rush to my banner with indomitable support.

263 Material wealth is not one of my goals, but I am a full time treasure seeker in my quest for new opportunities for my students to use their talents and in my constant search for those talents that sometimes lie buried in self- defeat.

264 And who do I have to thank for this wonderful life I am so fortunate to experience, but you the public, the parents.

265 For you have done me the great honor to entrust to me your greatest contribution to eternity, your children. And so I have a past that is rich in memories

266 I have a present that is challenging, adventurous and fun because I am allowed to spend my days with the future. I am a teacher……….. and I thank God for it every day.

267 Blooms Taxonomy COGNITIVE OBJECTIVES and ASSOCIATED VERBS KNOWLEDGE define state list name write recall recognize label underline select reproduce measure tell identify locate COMPREHENSION identify justify select indicate illustrate represent formulate explain judge contrast classify summarize match defend interpret compare infer generalize APPLICATION predict select assess explain choose find show demonstrate construct compute use perform apply prepare ANALYSIS analyze identify conclude differentiate select separate compare contrast justify resolve examine distinguish categorize SYNTHESIS combine restate summarize argue discuss organize derive select relate generalize conclude design imagine improve develop rearrange EVALUATION judge evaluate determine recognize support defend attack criticize identify avoid select choose recommend apprise compare assess decide argue consider

268 Thank You

269 Physics

270 What is Physics Physics is basically a science that attempts to understand nature and natural phenomenon. According to the wikipedia encyclopedia: Physics is the branch of science concerned with the discovery and characterization of universal laws which govern matter, energy, space and time. Its role, thus, is to provide us a logical picture of universe in agreement with experience. The learning and teaching of Physics, at the conceptual level, presents both an opportunity and challenge. Physics has supplied much of the driving force behind the science that, over the past four centuries, has permitted human understanding of the physical world to progress further and faster than at any time in recorded history.

271 Opportunity & Challenge The opportunity before a physics teacher, is, therefore, to convey the sense of interest, wonder and fascination, associated with all these developments, to the introductory student. The challenge arises from the fact that this sense of excitement, and interest, has to be conveyed against the backdrop of the often held perception that Physics is high on the list of most – feared classes by the general student population. It is a challenge, for all of us, to convey the wonders of the world of Physics in such a way that the apprehensive, science anxious student, is not intimidated by the presentation. This can perhaps be done best by highlighting and correlating the significance and the role of the basic laws and concepts, of physics in understanding and appreciating a variety of daily life phenomenon and very many natural observations.

272 Role in Society Physics is an elegant and beautiful amalgamation of philosophical thinking, reality and practical utility.It is perhaps the most pervasive of those reservoirs of human knowledge that we call as modern science. Physics has played an extraordinary and prominent role in shaping much of our current society. This is easily appreciated by realizing that, more often than not, it is the basic principles of physics that have helped mankind to develop, employ and use the vast variety of devices – computers, mobile phones, artificial satellites, robots, wireless communication, T.V., lasers, electricity generators, heat engines, ultrasound and MIR imaging and nuclear reactors, to name only a few – that have changed the culture of human society as a whole. Physics is thus very much relevant to all of us and as informed and enlightened citizens of the twenty –first century; we all need to have a basic understanding of the principles by which the physical world operates.

273 Atoms and Nuclei







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