Basic advice to undergrads: written assignments

Below is some basic advice I shared with my undergraduate class (Physics majors/Optics). This may be useful to other students here.

  • Do not copy a text verbatim, unless you are quoting the text as it is, with reference at that location.  If you use a source, then write a summary in your own words and cite the original source at the location of your text.
  • In the absence of primary data (which you generate originally), you will be using secondary sources such as research papers, books and internet content. For scholarly purposes (including assignments), it is better to use journal articles and books as references. Wikipedia is essentially a tertiary reference. Although some entries are good, wikipedia content is generally taken from a book or a research paper. Identify that source and use it for your assignment and reference. Directly citing wikipedia (which is usually not peer reviewed by experts) is not a general practice in scientific literature. 
  • When you take a figure or equation from a secondary resource (paper, book, internet), it is important that you cite the source in figure caption/equation location.
  • In an assignment, I am mainly interested in reading what you think about the topic under consideration. Feel free to put down your thoughts and compare and contrast it to the literature you use. This is where the thinking + learning happens.
  • For some general advice on referencing, especially for online communication, have a look at my blogpost.
  • To appreciate importance of written communication in learning, have a look at another blogpost.

A relevant book and its review

A book review has appeared an important and timely book on a topic which is subject to misinformation:

Are Electromagnetic Fields Making Me Ill? How Electricity and Magnetism Affect our Health, by Bradley J. Roth

reviewed by Robert G. Olsen in the most recent issue of the American Journal of Physics.

As the reviewer says:

“While the focus is on the specific controversies listed in the table of contents, an even more valuable contribution of the book is the description of Roth’s methodology. In describing his approach to evaluating the science (or lack thereof) behind each claim, you will learn some of the thought processes needed to evaluate any new technology. Anyone who adopts these approaches will become a better investigator of new claims”

I have been following book-reviews of American Journal of Physics
There are some really good recommendations and assessments.

53. Karnad’s preface to his memoir

One of the important aspects of reading a preface to a book is to know why an author wrote that book. This is one place where authors freely express their opinion on various things, and sometimes this opinion is not necessarily related to that book. For me, reading the preface connects me to the author in a better way than say, reading a review of the book, which I generally do after reading the book. Over the years, I have made it a habit to read the preface of almost any book I have come across.
In this context, recently I came across one of the most hilarious prefaces I have read. This is from Girish Karnard‘s memoir (translated from Kannada) titled : this life at play.

Below I reproduce the preface (which is by the way, available online) :

Dharwad, 1973

Aayi (my mother), Bappa (my father) and I were having lunch. My first film Samskara had won the President’s Gold Medal. My second, Vamsha Vriksha, had had a successful run and won the National Award for best direction. My latest film Kaadu was in the final stages of production. I was a Sangeet Natak Akademi awardee. And I had just been named the director of the Film and Television Institute of India. The air at home was thick with self-congratulation.

Then Aayi looked at Bappa and said, ‘And we had thought of not having him.’Bappa went red in the face. After some stammering, he managed to say, ‘That was all your idea, not mine. Why bring this up now?’ and hid his face in the plate in front of him.

I had to know more. I asked Aayi, and she explained: ‘I had three children already when I became pregnant with you. I thought that was enough, so we went to a doctor in Poona named Madhumalati Gune.’


‘She had said she would be at the clinic, but she wasn’t. We waited an hour and returned.’

‘And then?’

‘And then, nothing. We never went back.’

I was stunned. I was then thirty-five years old. Still, I grew faint at the possibility that the world could have gone on without me in it. For a while, I sat there unaware of my surroundings, considering the idea of my non-existence. A thought struck me. With some bewilderment, I asked about my younger sister: ‘Then, what about Leena…?’

Aayi said, somewhat coyly, ‘Oh, we had stopped thinking of all that by then.’ She burst out laughing. Bappa remained engrossed in the contents of his plate.

Had the doctor arrived at the clinic as promised, these memoirs and their narrator would not have existed. So, I dedicate this autobiography to the memory of the person who made all this possible: Dr Madhumalati Gune.

Girish Karnad

Bangalore, 19 May 2011

40. Tadashi’s practical application

Steven Strogatz is a well know applied mathematician from Cornell University, and has done some fascinating research on nonlinear dynamics (NLD). His lecture series on NLD and chaos is one of the best I have come across. Apart from writing columns in New York Times, he has also published some fantastic books on explaining mathematics, its relevance and impact on our daily lives, society and ecology.

Steve Strogatz has also been hosting The Joy of x podcast on the Quanta Magazine. In there, he interviews many contemporary mathematicians and scientists, who are actively involved in research and teaching. I found these informal interactions and exchange of ideas very interesting.

In one of the podcasts, Steven interviews Tadashi Tokieda, a mathematician who is interested in toys, and specifically the intriguing mathematics and physics of toys. In this interview, Tadashi describes his journey as an artist, philologist and as a professor who works on mathematics of toys.

Towards the end of the podcast (around 49 min in this audio), Tadashi describes how people (especially adults) ask him about the practical applications of studying toys, and how it can be beneficial to them. To this, his answer is something on the following lines :

When I show these toys to children, and explain to them the science and mathematics related to the toys, they feel very happy about it. What can be a better practical application that this !

Listening this just made my day…

26. Trinocular View of Science

When I come across any book, I do two things : first, I take a glimpse at table of contents, and second, I read the preface/foreword to the book. The second part is generally revealing in its own way, as I get to learn not only about the content of the book, but also about the human side of the topic under study. Recently, I was reading a technical book. In there, I came across a foreword written by Jacques Friedel, in which he quotes his grandfather Georges Friedel, and a part of the quoted text is reproduced below :

…none of the three approaches – the naturalist, the physicist, and the mathematician – should be neglected and that a healthy balance must be preserved amongst them !……

The text in bold is my emphasis. This quote resonates with what I think is a good way of doing science. Let me elaborate a bit on this “trinocular” view of science.

Photo Of Hands

Image courtesy : Pexels – Creative Commons License

  • Naturalist: In this approach, one can cater to the curiosity of the self by absorbing and observing nature. In a way, this approach helps you to connect with a phenomenon at a personal level with a touch of imagination of ones own. The feeling of wonder is what plays a critical role to be a naturalist, and a naturalist approach is to take this grasp seriously, and wonder about why nature behaves the way it does. In a way, most of the children are naturalist. Also, this approach, in my view, is one of the fundamental aspect of what makes us human : the ability to wonder and question.
  • Physicist (scientist to be more general) : Once you observe a phenomenon or intrigued by a fact, the questions to ask are: why and how such a thing happens? To answer these questions, you need to bring in the existing knowledge of science and look into the problem at hand through this metaphorical lens. You will have to ask to what framework of concepts does your observation belong to, and try to cast your naturalist observation in this light. This helps you to identify the scientific parameters of the problem, i.e., the dependent and independent variables. With this knowledge about parameters, you can not only probe the system under study, but also control it in a systematic way (first step to engineering). Such a control gives us an intellectual platform to construct hierarchical structures, which can further serve as foundation to new phenomena and structures.
  • Mathematician : This viewpoint brings in the analytical framework to the observations at hand. From the scientific thought – via hypothesis, experiments and models, we would have obtained some insight into a problem. These building blocks can be further refined and articulated in a precise language, such that we can generalize the problem to a larger set of questions which can go beyond the system under study. This transfer of real to abstract picture is what make mathematics so powerful. It catches the essentials of the problem, and facilitates a framework for generalization, which can be further applied to a new problem.

What I have discussed above is a way (not the only way) to approach research in natural science. Interestingly, the above 3 approaches need not be considered in chronological order. The inspiration to study a natural phenomenon or anything for that matter can be initiated from any of the 3 approaches. A question or an observation in any one framework can be cast as a query in any other framework, and that is what makes pursuit of science so wonderful.

Perhaps, the most important lesson from the Friedel’s quote is to keep a healthy balance of all the three approaches while studying a natural process. Importantly, this triangulation and extrapolation of approaches is how you build knowledge : be it engineering, medicine, public policy or any facet of epistemology. At the heart of all these approaches is to look at a problem from multiple viewpoints and be open to adaptation, criticism, and revision.

After all, depth in view needs more than one cue !

Letter to My Undergrad Students

This semester I was teaching an advanced physics lab course (4th year BS-MS). Below is an email I sent to them. You may find it interesting :


Image of a plasma discharge experiment in the UG physics lab at IISER-Pune

Dear Students of PHY430,

I hope all of you are doing fine and staying safe where ever you are. Given that we are part of an advanced lab course, compensating for the lost time via internet is not feasible. To fill in the gap, I am writing to you about something you may find interesting and useful. So here it is:

  • Ventilators : By now you may be very familiar with this terminology. Essentially, it is a medical device that helps you to mechanically breathe, and has turned out be a vital component in fighting the extreme medical cases of COVID epidemic. In this regard, I want to inform about the efforts of my colleagues Sunil Nair and Umakant Rapol, who are actively involved in design and development of low-cost ventilators. As you may recognize, both of them are experimental physicists, and their knowledge and intuition has been put to excellent use during the pandemic. In an essence, their involvement in this venture shows how a strong foundation in physics can not only solve deep queries in fundamental aspects of science, but also can cater to an emergency situation. This is one of the important lesson of this course : the skills and knowledge that you gain as part of experimentation in a lab can be transferred and implemented to solve problems outside a lab.
  • A Book recommendation: Talking about experimental skills, I thought of recommending an excellent book by Matthew Crawford titled “Shop Class as Soulcraft: An Inquiry Into the Value of Work”. This is a kind of an autobiographical exposition by the author, who majored in Physics, obtained a Ph.D. in political philosophy, and worked in policy circles of Washington D.C. for a brief period, and quit this job to become a motorcycle mechanic and an academic author. This book dives deep into the philosophy of why working with hands (and brains) is a deeply satisfying venture as a career and life-style. If you are not able to read the book, here is an excellent excerpt by the author himself.
  • Lab reports: Do send me the report of the experiments that are due to be evaluated. I know some of you may or may not have good access to internet, so timelines can be flexible (2 weeks from today). Also, you may not have access to research material. In that case, do co-ordinate with your lab partners, and let me know if I can be of some help in this regard.

Finally, keep your experimental spirits high. After all, everything at home is a kind of lab equipment to explore


Stay safe,


Expression as Exploration

How often I found where I should be going only by setting out for somewhere else.”
R. Buckminster Fuller

         About a month ago, I had an opportunity to interact with school students who were on the verge of transitioning from 10th and 11th grade. This event was part of a tech-fest organized by College of Engineering, Pune. The topic of discussion was “what scientist does in everyday life?” The students were very communicative (surprise!) and asked many questions (another surprise!), which was heartening. During the interaction, one of the issues we discussed was the importance of note-taking, as part of any serious observation in science, art or any other creative pursuit.

 One of the curious questions asked by a student was the following: “If there are so many technological tools that are available to us today, why should we at all write by hand? Why don’t we directly learn typing on a computer instead of handwriting?”

This was an important question, and I did mention that writing by hand has not only the benefit of processing thoughts more effectively, but also provides a sense of creation that may be lost while typing a text. Furthermore, symbolic representation, manipulation and thought processing – as done in mathematical thinking or calligraphy – is more conducive and convenient in the hand written form.

I also pointed out that there is some scientific evidence which indicates that handwritten notes have greater impact on processing the information in our brain, than when the same notes are typed on a device. I told that there is a form of elegance and individuality that a handwritten displays, which may not be represented in a text that is typed. I mentioned that writing in general and handwriting in particular, was not only a form expression but also as form of exploration. I indicated that just like music, writing has a psychological benefit of its own. It helps you to explore your thoughts and creates a sense of connection with oneself. Interestingly, it will also take you on a journey which you may not anticipate. The quote at the beginning of this blog sums it up nicely. Writing is a form of exploration, and by merely writing, we are taken to new worlds which we had not envisaged or planned to go.

In this blog I give 2 examples of a scientist and a writer, who have effectively used handwritten text in their work and have deeply impacted their respective fields. The choice is purely personal, as they are inspirational to me. Here we go….

Marie Curie

Curie photo
Image Credit : India Today

Cutting-edge science in early 1900s, especially in experimental physics and chemistry has had a great impact on modern society. Among the many who thought deeply about the nature of matter, Marie Curie’s contribution stood out. As a dedicated researcher, she not only developed elaborate experimental methods by herself to unveil the secrets of radioactivity, but also silently built a school of thought where dodgy, experimental exploration motivated new questions and directions in natural science. Below text is a snapshot from Marie Curie’s notes which describes the sample preparation in her lab. Interestingly, the mentioned texts of Marie Curie are still radioactive (and kept under isolation), and will remain radioactive for another 1500 year!

Marie Curie's notebook
Image credit : Wellcome Images

Virginia Woolf

VW image
Image Credit : Getty Images

A literary giant who is surely one of the pioneers of modernist thought process, kept a diary for herself all throughout her life. In my opinion she was a great humanist who redefined the art of narrative from a modern perspective. What’s more, her texts are so quotable that anybody who reads them will get a new viewpoint of the world which we had never seen. Below I reproduce a copy of her handwritten page of her famous book “A room of one’s own”. In this text, the story is still in the making, but you can see how a cluttered text at that time has evolved into a masterpiece now.

A Room of One's Own, by Virginia Woolf
Image Credit : Cambridge University

Well….preaching without practice is always hollow. When I was interacting with the students regarding handwritten text, they asked me whether I do write by hand. And my answer was yes, and below is a small handwritten note from my own notebook:

Snapshot of text from my notebook

Handwritten text has its own aesthetic value, and I believe it should be retained as long as human expression exists.

Virginia Woolf once famously wrote,

 “Thoughts without words… Can that be?”

last part modified

My Metaphoric Oxygen

There is no Frigate like a Book
To take us Lands away
Nor any Coursers like a Page
Of prancing Poetry –
This Traverse may the poorest take
Without oppress of Toll –
How frugal is the Chariot
That bears the Human Soul –

                             BY EMILY DICKINSON

Generally speaking, scientists are natural philosophers: they observe nature, ask questions, hypothesize an answer, test them through experiments and extend this exploration by escaping into the universe of ideas in books and journals. New ideas emerge from this exploration and join the chorus, and the intellectual journey continues. In my own research on light scattering, I have been deeply influenced by ideas of various fellow-explorers. For me, journal papers and books encompass the “metaphorical oxygen” for creativity and knowledge. Below I introduce you to some classic books which keep my research alive.

  1. Absorption and Scattering of Light by Small Particles
    • Author(s): Craig F. Bohren and Donald R. Huffman
      • Comments: There are two kinds of authors who write textbooks. One is the ‘boring kind’ and the other is the ‘Bohren kind’. If you want to fall in love with light scattering (and science in general), read books and articles by Craig Bohren. It will not only deeply influence your thinking, but also will show how a textbook can, and should, evolve a subject systematically. This particular classic has some of the most important ideas related to how light behaves when it interacts with matter comparable to the wavelength of light, and forms the bedrock on which a lot of contemporary research, including nanophotonics and plasmonics, is pursued. This book has wit, humour and a touch of poetry jumbled up together as flowing river of knowledge. To give you a spirit of their writings, let me reproduce the first paragraph of their introduction


  1. Light Scatteing by Small Particles
    • Author(s): H.C. van de Hulst
      • Comments: The first edition of this book was published in 1957, by the author was a legendary astronomer. This book has a beautiful description of single and multiple-scattering phenomenon, and describes specific situations where they apply. Written with an astrophysical viewpoint, it elegantly combines depth and breadth in a lucid way. This book has perhaps served as inspiration to most of the books written on light scattering.
  1. The scattering of light and other electromagnetic radiation
    • Author(s):  Milton Kerker
    • Comments: Some researchers have remarkable ability to choose problems that have far reaching consequences beyond the next research paper. Milton Kerker was one such legend. His research papers and this book has not only influenced the way physics of light scattering is studied, but has had deep impact on utilization of light scattering in various branches of science and technology. This 600 odd page book is indeed a masterpiece, and in a unique way caters to almost all kinds of researchers who are interested in light scattering.
  2. Dynamic Light Scattering with applications to chemistry, biology and physics
    • Author(s): Bruce J. Berne and Robert Pecora
      • Comments: A majority of the matter in biology and chemistry are suspended in a fluid. When an object in a medium undergoes Brownian motion, it influences the way a light beam scatters and traverses through that medium. This book explain the how and why of this fascinating topic. Written by experts in chemical physics, this classic serves as the foundation for light scattering in soft-condensed matter physics.
  1. Molecular Light Scattering and Optical Activity
    • Author(s): Laurence Barron
      • Comments: Historically, light scattering by molecules has been studied by legends such as Rayleigh, Raman and many more. Interestingly, all these legends emphasized the connection between polarization of scattered light and structure of matter. In this book, Barron puts together these ideas in a very elegant way, and motivates and develops the phenomenon of optical activity from a molecular physics viewpoint. Given that a majority of biomolecules are chiral in nature, the insight that one obtains by reading this book has direct implication in understanding the structure and dynamics of biomolecules such as amino acids, proteins and DNA.
  1. Scattering, Absorption, and Emission of Light by Small Particles
    • Author(s): MI Mishchenko, LD Travis, AA Lacis
      • Comments: Mischchenko is a scientist at NASA, and his books on light scattering have had great influence in aerosol science, radar technology and many more. The T-matrix codes based on this book forms a very important tool across the research community that works on weather prediction and pollution monitoring.
  1. Wave Propagation and Scattering in Random Media (Vol 1 and 2)
    • Author(s): Akira Ishimaru
      • Comments: This classic from late 1970s was one of the elaborate attempts to put together wave propagation and scattering in a random media on a rigorous mathematical foundation. This 2 volume book has solutions to various mathematical problems that one encounters in light scattering physics, and makes an important connection to transport theory of light in a medium.
  1. Optical Scattering Measurement and Analysis
    • Author(s): John C. Stover
      • Comments: If you are interested in experimental aspect of light scattering, this is one of the best books. It is essentially a field guide, which tells you how to quantitatively make a light scattering measurement, and what aspects to look-out for. This is a very good book for students who want to get a hands-on experience in light scattering.
  1. LASER LIGHT SCATTERING, Basic Principles and Practice
    • Author(s): Benjamin Chu
      • Comments: Chu’s book develops the topic of laser light scattering in terms of both experimental aspect and theoretical foundations. Importantly, it connects the topics of light scattering to optical spectroscopy, and shows how one can obtain meaningful information about light-matter interaction.
  1. Mesoscopic Physics of Electrons and Photons
    • Author(s): E. Akkermans and G. Montambaux
      • Comments: Quantum mechanical entities such as electrons and photons can be confined in space and time. Depending on the geometry of confinement, very interesting physics such as weak and strong localization can emerge. This book looks at the physics of confined electron and photon from a unified viewpoint. It highlights similarities and difference between the electrons (fermions) and photons (bosons).
  1. The Raman Effect: A Unified Treatment of the Theory of Raman Scattering by Molecules
    • Author(s): Derek A. Long
      • Comments: Written by a pioneer in the field, this book till date remains the most rigorous treatment on Raman scattering of light from a theoretical viewpoint. Based on quantum mechanical arguments, this book relies on perturbation theory, and clearly shows the connection between structure of molecules and how they influence the scattered light.
  1. Principles of Surface Enhanced Raman Spectroscopy and Other Plasmonic Effect
    • Author(s): Eric C Le Ru and Pablo G. Etchegoin
      • Comments: The most definitive book written on surface enhanced Raman scattering by two physicists whom I greatly admire. This book gives unified treatment of plasmonics and surface enhanced inelastic light scattering, and is written in a style catering to physics audience. The book has a lot of details and explanations, and also serves as excellent introduction to plasmonics and vibrational spectroscopy. Given that the authors themselves are pioneers in single-molecule Raman scattering, their insight into single molecule optics in plasmonic field is fascinating. Unfortunately, Etchegoin succumbed to cancer, and I could never meet him. However his great ideas and thoughts stay on…
  1. Introduction to Wave Scattering, Localization and Mesoscopic Phenomena
    • Author(s): Ping Sheng
      • Comments: Random lasing is an emerging topic of research in nanophotonics. The fact that one can have random structures assembled in space and time, and yet achieve spatial and temporal coherence is quite remarkable. This book brings together insights from wave scattering and mesoscopic physics to show how light behaves when confined to small volumes compared to wavelength of light. The insights obtained from this book are heavily used in the literature on random lasers.
  1. Fundamentals of Atmospheric Radiation
    • Author(s): Craig F. Bohren and Eugene E. Clothiaux
      • Comments: Bohren weaves his magic…..again. Although the title of this book indicates atmospheric radiation, the way the authors treat the topic of absorption, emission and scattering of light is fascinating. This book gives a broad viewpoint of interaction of light with matter, and shows one can and should treat the subject coherently. The references and problems are very relevant and interesting, and I have found some gems while reading through this text.