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. https://aapt.scitation.org/doi/full/10.1119/5.0107970

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.

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.

Born and Wolf

Born google
Image courtesy: Google

BORN AGAIN: Today I opened the google webpage and to my surprise found the doodle (picture above) celebrating birthday of Max Born. He was not only a great physicist who contributed immensely to quantum mechanics and other branches of physics (including optics), but also a mentor to many great physicists including Fermi, Heisenberg, Pauli, Wigner, Teller, Emil Wolf and many more.

Every student who has studied physics, is aware of quantum mechanical wavefunction (ψ). Given a quantum system and its environment (electron in an atom, for example), wavefunction is a fundamental quantity that one can compute, and forms the basis to understand the system in greater detail. When quantum mechanics was evolving in early 1900s, the question of how to physically interpret the meaning of wavefunction was at the forefront. It was Max Born who gave the statistical interpretation for the wavefunction, which later fetched him a Nobel prize in 1954.

Born identified the importance of interpretation of the wavefunction, and its connect to the realistic, observable parameter. To quote Born from his Nobel lecture :

“The problem was this: an harmonic oscillation not only has a frequency,
but also an intensity. For each transition in the array there must be
a corresponding intensity. The question is how to find this through the
considerations of correspondence? “

This quest set-forth an intense programme in physics and motivated people like Heisenberg, Schrodinger, Bohr, and Einstein to search for an answer. Interesting, Born’s work was heavily inspired by Einstein’s work. To quote Born from his Nobel lecture:

“But the decisive step was again taken by Einstein who, by a fresh
derivation of Planck’s radiation formula, made it transparently clear that the
classical concept of intensity of radiation must be replaced by the statistical
concept of transition probability.”

Further, he adds

“Again an idea of Einstein’s gave me the lead. He had tried to make the duality of particles light quanta or photons – and waves comprehensible by interpreting the square of the optical wave amplitudes as probability density for the occurrence of photons. This concept could at once be carried over to the ψ-function: |ψ|^2 ought to represent the probability density for electrons (or other particles).”

Reading Born’s Nobel lecture, two things struck me : first was that science is never done in isolation. Every single idea is inspired by another idea. Second,  physical optics has a major influence on interpretation of quantum mechanics. Max Born was no stranger to optics. In fact, he was one of the pioneers of classical optics, and I am not surprised that he could make some vital connections between physical optics and quantum mechanics.


BW book
My personal copy…..standing tall and heavy 🙂

THE BOOK: This brings me to the most famous book written in optics(see picture above) by none other than Max Born and Emil Wolf  (Emil Wolf was the last research assistant of Max Born, and a well know optical physicist) The book is titled “Principles of Optics”, but in optics community we call it “Born and Wolf”. The first edition of this book appeared in 1959, and has never gone out of print. Currently, it is in its 7th edition and is 951 pages thick !

As described in the preface (first edition of Born and Wolf), several people urged Born to translate his 1933 book: “Optik” from german to english. By 1950s, optics had evolved and had made inroads into atomic physics, molecular spectroscopy, solid-state physics and various other branches of science and technology. So, they had to write the book from scratch taking new ideas into consideration.

“Born and Wolf” explains optical phenomenon through the eyes of Maxwell’s theory, and has become the foundation on which various aspects of classical optics can be studied in a mathematically rigorous fashion.  In fact, it also lays foundation to various quantum optical phenomenon including coherence and correlation functions, on which Emil Wolf’s contribution has been immense.

For me, chapter 13 on “Scattering from homogeneous media” is the highlight of this book. It starts with elements of scalar theory of scattering by expaining the first-order Born approximation followed by discussion on scattering from periodic potential. The best part is the discussion on multiple scattering, which in a sense lays the foundation to study various important optical phenomenon including diffraction tomography and optical cross-section theorem (or more famously known as Optical theorem). Also, the 13th chapter has a very interesting discussion on concept of far-field and its connection to scattering of electromagnetic waves.

Actually, the book is very well known for its treatment on diffraction theory and image formation. It gives a very strong footing to attack problems in imaging, aberration and inteferometry using Maxwell’s equation and related boundary condition. It also, highlights optics of metals, which has now transformed and evolved into a sub-field of optics and photonics – plasmonics.

Origins of the book: The writing of this book has a historical context. Emil Wolf was a research assistant (post-doc) of Max Born and joined him after his Ph.D. He recollects his experiences with Born and about writing this book in an interesting article.  Below is an interesting quote:

“Through Gabor I learned in 1950 that Born was thinking of preparing a
new book on optics, somewhat along the lines of his earlier German book
Optik, published in 1933, but modernized to include accounts of the more
important developments that had taken place in the nearly 20 years that
had gone by since then. At that time Born was the Tait Professor of Natural
Philosophy at the University of Edinburgh, a post he had held since 1936,
and in 1950 he was 67 years old, close to his retirement. He wanted to find
some scientists who specialized in modern optics and who would be willing
to collaborate with him in this project. Born approached Gabor for advice,
and at first it was planned that the book would be written jointly by him,
Gabor, and H. H. Hopkins. The book was to include a few contributed
sections on some specialized topics, and Gabor invited me to write a section
on diffraction theory of aberrations, a topic I was particularly interested in
at that time. Later it turned out that Hopkins felt he could not devote
adequate time to the project, and in October of 1950, Gabor, with Born’s
agreement, wrote to Linfoot and me asking if either of us, or both, would
be willing to take Hopkins’ place. After some lengthy negotiations it was
agreed that Born, Gabor, and I would co-author the book.”

Wolf writes about Born and his working style:

“In spite of his advanced age Born was very active and, as throughout all
his adult life, a prolific writer. He had a definite work routine. After coming
to his office he would dictate to his secretary answers to the letters that
arrived in large numbers almost daily. Afterward he would go to the adjacent
room where all his collaborators were seated around a large U-shaped
table. He would start at one end of it, stop opposite each person in turn,
and ask the same question: “What have you done since yesterday?” After
listening to the answer he would discuss the particular research activity and
make suggestions. Not everyone, however, was happy with this procedure.
I remember a physicist in this group who became visibly nervous each day
as Born approached to ask his usual question, and one day he told me that
he found the strain too much and that he would leave as soon as he could
find another position. He indeed did 80 a few months later. At first I too
was not entirely comfortable with Born’s question, since obviously when one
is doing research and writing there are sometimes periods of low productivity.
One day when Born stood opposite me at the U-shaped table and asked,
“Wolf, what have you done since yesterday?” I said simply, “Nothing!” Born
seemed a bit startled, but he did not complain and just moved on to the next
person, asking the same kind of question again.”

Wolf also gives an account of why Gabor pulled-out, and how Wolf had to play an unexpected, but vital role in writing this book:

“…..Gabor soon found it difficult to devote the necessary time to the project, and it was mutually agreed that he would not be a co-author after all, but would just
contribute a section on electron optics. So in the end it became my task to
do most of the actual writing. Fortunately I was rather young then, and so
I had the energy needed for what turned out to be a very large project. I
was in fact 40 years younger than Born. This large age gap is undoubtedIy
responsible for a question I am sometimes asked, whether I am a son of the
Emil Wolf who co-authored Principles of Optics with Max Born!”

Wolf also praises Born’s open-mindness to various branch of physics:

“Optics in those days-remember we are talking about optics in pre-laser
days-was not a subject that most physicists would consider exciting; in fact,
relatively little advanced optics was taught at universities in those days. The fashion then was nuclear physics, particle physics, high energy physics, and
solid state physics. Born was quite different in this respect from most of his
colleagues. To him all physics was important, and rather than distinguish
between “fashionable” and “unfashionable” physics he would only distinguish
between good and bad physics research.”

Emil Wolf is now 95 years old, and is still a very active researcher. His recent paper was in 2016 on partially coherent sources and their scattering from a crystal. Wolf’s books are classics in optics, and continues to raise probing questions and important connections in sub-branches of optics.

In an essence, great science books are written with love and passion to communicate the excitement of science. Born and Wolf certainly does that, and continues to inspire us to learn optics from the masters themselves.

To conclude, let me quote Born himself from his Nobel banquet speech:

“The work for which the Nobel Prize has been awarded to me is of a kind which has no immediate effect on human life and activity, but rather on human thinking. But indirectly it had a considerable influence not only in physics but in other fields of human endeavour.

This transformation of thinking in which I have taken part is however a real child of science, not of philosophy: it was not the result of speculation, but forced upon us by the observed properties of Nature.”

Max Born and Emil Wolf, your work and your books have transformed our thinking, and the way we see light and matter. Thank You !