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IAPT is a grass-root organization working for the upgradation of Physics teaching and Physics teachers by conducting various academic programmes and activities, throughout the country.
Articles Submitted by our Members
e-Resources for Effective Teaching of the Topic “Atomic Structure”

Dr. Ranjana Abhang

abhang95@yahoo.co.in

E-resources e.g. computer simulations, animations can be integrated with usual lectures for communicating the topic effectively. Even the lectures can be delivered with power-point presentations instead of using the conventional method of blackboard and chalk. It is illustrated as follows

Topic: Atomic Structure

1. A powerpoint presentation by S.Morris (2006) on the site www.worldofteaching.com contains 18 slides which give the History of Atom from Democritus, John Dalton, Thompson, Rutherford till Bohr. Two ways of Representation of Atomic structure are explained with diagrams: 1. Electronic Configuration 2. Dot and Cross Diagrams of some elements (Not known much).

2, An Animation on the Bohr’s Model is on the site www.learnerstv.com by David H. Harrison (2003). It uses Macromedia Flash Player. Orbits of Hydrogen Atom, Excitation of electron to higher orbit by incident photon and emission of photon when electron returns to ground state can be seen. By selecting from five values of excitation photon energy, transition to different higher levels can be seen .

3. An interactive simulation using Java is on the website of University of Colorado at Boulder http://phet.colorado.edu/simulations. During the experiments photons /alpha particles are shooted at the atom and “what really happens” can be seen. Light controls using white and monochromatic light of different wavelengths are available for performing the virtual experiments. Prediction of the results according to six atomic models (1. Biliard Ball model, 2. Thomson’s Plum Pudding Model, 3. Classical Solar system model, 4. Bohr’s model; 5. De Brogli model using the wave particle duality, 6. Schrodinger’s model using concepts of Orbital quantum number and Magnetic quantum number). Energy level diagram is drawn and a spectrometer shows the spectral lines in the experiment for each model. Provision for varying the speed of actions (from low to high) is also available.

4. Learning Projects

The website http://www.thinkquest.org/library/ contains a library of 7000 projects created by students which won awards in ThinkQuest Competition. One of the projects is “Journey into the Atom” by Rahul Jain and Shaheen Gandhi (1997), Bridgewater, NJ, USA. Students can be encouraged to do similar projects and participate in the global competition.

Software installation needed to use e-Resources can be downloaded from sites as follows

Java 1.5 or higher from the website of Sun Microsystems Inc., www.sun.com

Adobe Macromedia Flash player from http://www.soft32.com/

Similar information on various topics will appear in the bulletin every month. The teachers are requested to give a feedback on the utility and the response of the students to the material on the website.

 

3. E-RESOURCES FOR EFFECTIVE TEACHING OF
“DOPPLER EFFECT”
 
Ranjana Abhang
 
Doppler Effect (DE) prevails in various situations-from siren on moving cars/train whistle to sonic boom of airplanes to cosmic redshift. The topic is usually a part of physics syllabus at +2 level (Junior college). Some e-resources to make it interesting follow
 
physics.msuiit.edu.ph/.../spvm2006presentations/Doppler%20effect.ppt-
Site of Western Mindanao State University, Philippines, has a powerpoint presentationby Angelourd T. et al. After the statement, DE  is explained for 4 situations 1) Source (S) & Observer (O) both stationary; 2) S stationary, O moving 3) S moving & O stationary 4) S & O both moving. In each case diagrams and formulae are given for 2 directions of motion-Away & Towards.    
 
http://msowww.anu.edu.au/~pfrancis/roleplay/MysteryPlanet/doppler.ppt#339,11,Example- Australian National University (ANU) gives apowerpoint presentationon application of Doppler Effect in Astronomy.  The background information about importance and uses of spectroscopy in Astronomy, electromagnetic spectrum, spectrograph etc. is followed by a colored graph showing the effect of motion of distant object (star) on colour in the spectrum with applications in deducing the direction of motion of stars, radar, speed traps
 
An animation by Walter Fendt shows that as an ambulance with a siren approaches / goes away from the observer, the wavefronts reach the person in shorter /longer intervals respectively.
 
Learners TV site shows animation by D.M.Harrison (2007). Wave fronts of a moving source depend upon observer’s position & change as speed of source is varied- speed of wave is constant
Learners TV site shows a series of 8 animated scenes by D.M.Harrison (2003): DE for moving sound source (car); Process of hearing sound; Graphs of Source (Tuning fork) amplitude & Detector (ear drum) response versus sound pressure for different cases: Source stationary and detector moving towards & away, with velocity <= sound; Detector stationary and source moving; Formulae relating source & detector frequencies covering  above cases
 
University of Virginia site displays a flashlet by M. Fowler. A moving source emits circular waves. The speed of source can be changed & ratio of speed of source to the speed of wave, (i.e. the Mach number) is controlled by a slider giving shockwave for Mach number>1. The changes are seen in the picture of wavefronts as well as in sound heard using microphone.
Notes by M. Fowler (2008) for above flashlet contain derivations of formulae for various combinations of motions of sound source & observer, relativistic equation for Doppler shift using light.
 
Site Ion-capa has Java applet by W. Bauer (1999) for DE visualization. By dragging the mouse, source velocity (represented by arrow) is changed. Exact value of Mach number is displayed numerically.
 
University of Geogia (UGA)- Difference in pitch (sound)/ colour (light) to 2 observers on 2 sides of a moving source.
 
University of British Columbia, Canada, displays an interactive java simulation with instructions for its working. By clicking on “Run Animation” button, waves are started. Source motion can be disabled (ie. stationary) or enabled to be linear / circular / bounce motion; Source speed can be changed as faster/slower/ reverse/ mach; Sound speed can be decreased /increased.
 
Kettering University site shows an animation by D. A. Russell, for stationary observer and moving source. Wave fronts for three cases are illustrated: Vsource < Vsound,   Vsource= Vsound,  Vsource> Vsound (with Mach cone and sonic boom created by supersonic jet trainer braking sound barrier)Frequencyshift formula, Mach no. & explanation for each case, links for applications of DE e.g.  Doppler Radar, Echocardiography, Radio Direction Finding System are given.
 
DATA Site of University of Illinois, illustrates the concepts of Red and Blue Shifts by color of light waves. Intermediate steps of change in velocity of the source are followed by gradual change in frequency and colour of waves. Formula for wavelength change for light is given.
 
A simulation by S. Maus & D. Roth (2002). Change in source frequency moving with constant velocity depends on observer’s position.  By moving the mouse, mouse position, elapsed time t and wave period T are displayed on a graph paper. This Applet is "scriptable" i.e. it can be configured and controlled by using JavaScript methodse.g. Wave phase velocity, emitter velocity relative to wave phase velocity, wave period and time step for numerical calculation can be varied
 
http://www.youtube.com site of You Tube presents a variety of videos with commentary.
Special points of some are cited below. Time duration (minutes seconds) given in bracket
http://www.youtube.com/watch?v=a3RfULw7aAY&NR=1 “DE using Car Horn” (9”) &
http://www.youtube.com/watch?v=imoxDcn2Sgo “DE-Fire Engine siren” (18”) by David Robert- changes in sound pitch with direction of moving sources (away/towards observer)     
http://www.youtube.com/watch?v=4mUjM1qMaa8 “DE- Listener in Motion” by Pelletier Physics (25”)-changes in pitch as listener moves towards / away from a stationary source
http://www.youtube.com/watch?v=RsiY8VdDlDQ “DE-3D Animation” by Paulie(4’:42”) Basic relations between pitch, frequency & wavelength; Applications e.g. Doppler Radar
http://www.youtube.com/watch?v=-t63xYSgmKE “SLight” (2’:33”) DE for Sound (Car) and Light (Star) both- sources receding / approaching observers: change in pitch & colour
http://www.youtube.com/watch?v=n4BHA1hHjDc&feature=related “Red and Blue shifts of light” (12”) seen by an observer in receding /approaching parts of a rotating galaxy.
http://www.youtube.com/watch?v=FhfnqboacV0 “What is Redshift”-Tom Jarrett of IPAC Caltech (2’:30”): Use of DE to measure distances of stars in the expanding universe.
http://www.youtube.com/watch?v=Man9ulEYSgk–“Red Shift” by fizzics organization (2’)-Examples of water, sound & light waves, cosmic red shift in spectra, Big bang theory   
 
http://journal.lapen.org.mx/jan08/LAJPE-125Final%20Gimenez.pdf site has an article by Marcos H. Giménez et al (2008) in Latin American Journal on Physics Education showing animation process of the space-time visualization explains DE, Sound barrier etc.
 

Thus e-resources bring life and interactivity to the concepts and enhance understanding.

 

e-Resources for Effective Teaching of  Interference of Light
Dr. Ranjana Abhang
 
Interference of Light is a significant phenomenon in physics. A large number of e-resources related to it are available on the internet. Some of them are cited as follows
 
A powerpoint presentation giving the summary of Interference is on the website of University of Aberdeen, UK [1]. It contains 30 slides briefing on topics-Interference fringes, Constructive and Destructive Interference-Mathematical conditions, Fringe visibility, Young’s double slit interference, its explanation with phasors,  comparison of interference due to 2 and 50 slits, Thin film fringes, Haidinger and Fizeau’s fringes, Michelson Interferometer, Lloyd’s Mirror etc.
 
A powerpoint presentation “Two source interference” is given by Sylvia (2005) on site
of World of teaching [2]. Constructive and Destructive Interference and the conditions for their occurrence in terms of path difference are explained with diagrams on 6 slides.
 
In addition, in many powerpoint presentations, videos etc. related to the “Waves”, “Wave nature of light”, some slides referring to the phenomenon of Interference are present.
 
Lecture demonstrations on different subtopics of interference are given by University of California Berkeley [3]. Sketches of experimental set-ups, apparatus with labeled components, resultant patterns etc. are drawn giving explanations. They include interference due to double slit by visible light, microwaves and laser beam (through cornell slit-film);  Lloyd’s mirror, Michelson Interferometer fringes, Interference in Oil film on water and in Soap film, Ripple Tank with plane and spherical water waves, Newton’s rings by transmission and reflection etc.
 
An interference pattern with bands of constructive and destructive interference created by two sources is shown explaining the concept of path length difference on the site of Boston University, USA [4]. Applet at site of PhysicsLab [5] has similar nature.
 
Similar interference pattern is presented at University of California, Los Angeles (UCLA) USA site [6] by Wolfgang Christian. Its special feature is that it produces interference patterns using more than two sources also for varying wavelengths of light sources.
 
A simple interactive Java applet for two slit interference is given by Michigan State University, USA [7]. The graph of intensity versus distance along the screen is plotted for different values of slit separation and wavelengths of light source.
 
An Animation on Young’s Interference experiment (using Adobe Shockwave player) is created by Fast Track at Victoria Junior College (VJC) of Singapore [8].Wavefronts from two secondary sources (slits) derived from a single primary source produce interference bands on a plane screen. The intensity at each point of the resultant wavefront is plotted alongside the bands. Effect on the interference bands and the intensity is observed by varying parameters e. g. Screen distance (2-5 meters), Wavelength of light source (380-750 nm), diameters of  slits (0-0.1 mm) and their separation (0.5-1.5 mm).
 
A similar animation (flashlet) is presented by University of Virginia, USA [9]. Two waves (created by dragging point sources of visible light or the detector at the plate) and the algebraic sum of their amplitudes (i.e. resultant) are shown with two point sources. By pressing “play” a trail of light spots (representing the two-slit interference pattern build up by adding two waves sequentially) is created at the plate. Step size is adjusted with “trail step” slider. The intensity of the resultant of waves is represented by the brightness of light spots. Values of wavelength, amplitude, source to plate distance and the distance between sources are recorded and can be changed by a slider. Path difference vector corresponding to each location of the light spots is shown and its value is noted.
 
An animation [10] by Walter Fendt (2003) has a distinguishing feature that the screen is semi-circular instead of being plane. The interference patterns of different orders obtained by changing the wavelength of source or the spacing between the slits, are shown on the screen and also on a linear angle scale (-900 to +900). The values of angles for maxima and minima corresponding to different orders are recorded in two boxes. The locations of the current angle are shown by arrows when angle is varied in the range 00-900. Alternatively, the points of minima are shown by red dots in the intensity profile at the bottom. Value of the relative intensity in the interference patterns corresponding to each angle position is also recorded. Equations giving conditions for maxima and minima of different orders are stated.
 
An interactive simulation using Java on the website ofUniversity of Coloradoat Boulder [11] is useful to learn the abstract properties of light by analogy with water or sound waves. First wavefronts using one and two sources in the form of drip/s of water, loud speaker/s or source/s of light are created. Their secondary sources are created by inserting slit/s. By using two sources of waves or inserting two slits, interference patterns are obtained. The patterns change as the amplitude and frequency of the sources and the width, location and separation of the slits are varied. Screen chart shows a graph of intensity versus position. By adding a detector, graphs of water level, sound pressure or electric field, versus Time  are plotted. By pressing “Show graph”, plots of these quantities versus position are seen. The simulation emphasizes the characteristics that are common to all types of waves.
 
With such e-resources, students experience that “Physics is Fun and not a subject to shun”
 
References

IAPT Website: Request for Content Contribution

As per the discussion in the General House at IAPT Conference in Bangalore and subsequent discussion with President, General Secretary and other IAPT EC members, the beta version of the IAPT website has been launched since 20.1.2009. All the members are requested to browse the web site and give their valuable comments/suggestions about the structure of the website to meet the expectations, needs and its reach among the target groups. The URL of the website is:

www.indapt.org

The content of the web site needs to be updated on various pages, which is being undertaken after getting information from various sources within the framework of IAPT. However, to begin with, for the following links on the website content is solicited from all the members. These are listed below:

  1. Web links submitted by the members: These are the useful links under various heads found by the members and can benefit the physics teachers, students and researchers

    1. Physics related links
    2. Physics Education related links
    3. Physics Education Research related links
    4. Physics e-resources
    5. Free down loadable physics e-books
    6. Physics Simulations
    7. Physics virtual laboratories
    8. Open Coursewares in physics for schools, colleges and universities.
    9. Information about different activities in various areas of physics, such as conferences, symposia, conventions, workshops and schools
  2. Articles submitted by the members: Under this link articles on various topics are invited under various themes related to
    1. IAPT and its work and people in the last 25 years in a reminiscent mode especially by founder members, senior members, past presidents, past general secretaries and other involved people
    2. Picture gallery of the mile stone events/ people of the last 25 years of the IAPT work
    3. Time line of the various activities of IAPT.
    4. Picture gallery of Noble laureates in Physics with small write-ups
    5. Articles related to developments to be organized in various categories such as

i. Physics research at the frontiers

ii. Physics education research

iii. Innovative ideas in curriculum development

iv. Profiles of Physics teachers, researchers and innovators


3. Quote of the day: It is a collection of quotes by eminent physicists, scientists for display on the home page of the web site. You can send such interesting quotes to create a repository to be displayed randomly under this title
4. A separate format is being devised to display information related to various activities of the regional/ sub council by Dr. Bhupati Chakravarti.

 

Please send your feedback, contributions on all the above points at the following e-mail address:

pk_ahluwalia7@yahoo.com

 

Your contributions can really help the site to evolve over a period of time as a useful link to connect with each other meaningfully.

REMINISCENCES OF PROFESSOR BABU LAL SARAF

Babu Lal Saraf was an experimentalist par excellence who felt deeply for sound understanding of the basic concepts of Physics. He worked at the ground level, caring for students and associates alike. His enthusiasm and zest in evolving a novel program ‘ Physics through Experiments’ was truly amazing. He got the willing assistance of his colleagues like Prof. S. Lokenathan and Prof. D.P. Khandelwal to name a few. He conceptualized a modular approach in developing various laboratory experiments in mechanics, optics and nuclear physics, to avoid duplicity of apparatus required. He designed and fabricated a unique Air Track bench to demonstrate and conduct a variety of experiments in mechanics. He cared to teach about precision and accuracy in his experiments in a way relevant to the understanding of the phenomena under investigation. No doubt soon his efforts brought him laurels through national and international recognition by way of UNESCO award. It led to the demands from institutions in the country and abroad for multiplicity of the apparatus. In the process, he wrote two guideline books on ‘Physics through Experiments’, explaining step by step procedures to conduct the individual experiments in an open manner, with emphasis on concepts involved. There is not an iota of doubt about the ingenuity of his approach towards conducting physics lab experimentation, far from the stereotype approach of black box approach hitherto followed. Truly it was a ‘Master Experimentalist’ approach. Some of the conventional teachers who themselves were never clear about the concepts involved found it hard to comprehend his approach that was based on emphasis of the foundational aspects.

Babulal was born in Badnawar, Madhya Pradesh in December, 1923 and breathed his last in Jaipur on 01 March, 2009. He graduated from Maharaja College, Jaipur and earned his Masters degree from Agra University in 1949. After a short spell of teaching he left for doctorate research at the Bartol Research Foundation of the Franklin Institute in Swarthmore, Pa ( USA) in early 1950’s. He so impressed the senior physicists there with his experimental acumen that a series of Indian students followed later to that institute for doctoral research. It may surprise many that most of experimental nuclear physics related programs were developed in the Indian universities like Delhi, BHU, Kurukshetra, Punjab, Aligarh, Jaipur and Udaipur were by such Bartolian’s Indians. Prof. Saraf designed and fabricated a magnetic spectrometer at Bartol that was later used for another decade by a host of researchers. His own study was on ‘Inner Bremsstrahlung Spectra following e-capture’ that earned him the doctorate degree from Agra University in 1958. A light mention may be made here of an incident that happened to Saraf during his days at Bartol. As he use to work hard in the lab., he often had to go to market for his grocery needs at night time. The Police there saw him drinking from a bottle on a pathway only to be surprised that it was milk to quench his thirst, as he was a lone walker at that time!

On return from USA, he was offered a job by Dr. Homi Bhabha at the new Centre for Atomic Research he was establishing at Trombay. I first met him there in 1957 as I wanted to get his guidance about the offer I received from Bartol to complete my doctorate there, as facilities in Delhi University were far from adequate in nuclear research. He was engaged in building a Multi-channel Analyzer from scratch there. It was a sophisticated Instrument that hardly anyone dared to fabricate in India of those days. His ingenuity and experimental skill were outstanding. When he received an offer of a senior faculty position at Rajasthan University, Bhabha willingly allowed him to take with him all the equipment that he had built for his experiments, to the University. Such was the status of leadership and vision in those days in our country. Prof. Saraf was soon made Professor & Head, Physics dept. at Jaipur.

Prof. Saraf soon discovered how stereotype were our teaching Labs. in the colleges and universities. Though he was successful in carrying some frontline research work at Jaipur with the nice equipment he carried from Trombay, his mind compelled him to do something about the laboratory system and infrastructure that existed in the universities. He took up the task of building modern workshop facilities that would enable the teachers to design and fabricate experimental equipment to innovate and rejuvenate the stagnant system. Soon he could establish a working group of his associates and upcoming students. His home provided the open house for one and all, thanks to the ever-smiling and willing nature of Mrs. Saraf. As I had occasions to visit Jaipur on many occasions, I have never encountered such an open atmosphere of informal working while doing serious Physics.

Several unique open-ended experimental systems were evolved to conduct foundational experiments in mechanics, optics and atomic and nuclear physics. Detailed manuals were prepared to conduct each experiment to the satisfaction of the natural curiosity of a genuine student of Physics. Basic component units like Air track channels for collision studies, assorted compound pendulums, pulse and waveform generators, ac and dc regulated /variable power

supplies were designed and fabricated , with modern look and convenience in operation. The contributions were soon recognized nationally and internationally, as the professor was invited to an International meet organized by UNESCO. He won highest commendations there for some of his unique equipment. The experiments were not only demonstrative but cared to instill the significance of estimating accuracy and precision of measurements. Soon the University Grants Commission took note of these developments. Grants started to follow and a special centre was established for the Development of Physics Education at Jaipur. Prof.Saraf organized a unique International Conference on ‘ Physics Education Through Laboratory Experiments ‘ that was sponsored by national and international agencies.

On his retirement in mid 1980’s from University of Rajasthan, Professor Saraf continued to remain actively associated with the Centre for Development of Physics Education. Sponsors came by from private sector to duplicate his unique experimental equipments, as demands poured in from Colleges and Universities. Professor Saraf undertook several visits to institutions throughout the country for long time intervals, taking his caravan of equipment with least care about his personal health and comfort. Later on, he was invited by the IPS Academy of Indore to establish a special Institute for Science and Laboratory Education ( ISLE ) that was duly recognized by Devi Ahilyabai University at Indore as its post-graduate and research centre for award of the higher degrees. He was designated as Eminent Professor cum Advisor for life at that Institute. Inspite of his health problems he zest for work appeared insatiable. He was truly a karamyogi of highest degree, who worked till his death at the age of 85 years for the sake of bigger cause than personal ambitions!

Under the sponsorship of the Department of Science & Technology and with the cooperation of Bharat Vigyan Prasar Sansthan, a contract was given to prepare a audio-video film on the Life and Works of Professor Saraf. Several versions of the film are available lasting from 20 minutes to one hour. A special function was arranged on 11 July, 2007 at the Interuniversity Accelerator Research Centre (IUAC), formerly known as Nuclear Science Centre, New Delhi, to honour Professor Saraf in the presence of his family and distinguished guests. It was a well organized function where Professor Yash Pal came to extend an honour to this unique personality in Indian Science. It will be hard to believe in future that such a personality that lived simply but worked in a thoroughly professionally manner existed amongst us in flesh and blood. Some one called him in 2006 as ‘The Raman of Rajasthan’. May I say that his personality was unique in many ways through his transparent simplicity that radiated everything creative or innovative, enough to inspire young and old alike. I personally will remember him as academic mentor worth emulation in many ways yet unknown!

 

Narendra Nath
Former Professor and Head,
Physics Dept.
Kurukshetra University
259, Sector 7,
Urban Estate,
Kurukshetra-136118.
narendranath32@gmail.com
or
nnath32@ymail.com