Introduction to Electrodynamics
Book Description
Review:
This electrodynamics text for advanced undergraduate and graduate level students owes its origin to the meeting of two teachers nearly twelve time zones apart, one from the rolling prairies of Alberta in Canada and the other at the rugged hills of Pune in India. Clearly, they found both common problems in teaching, and a common approach to solving them. They also clearly share a common passion for a subject they describe in their preface as "wonderful and venerable", which they would like to make more accessible to students. This reviewer, himself a veteran of half a dozen attempts to teach this subject, would concur with many of the choices they have made. They have chosen a style which is by and large unhurried, explicit, and self contained, in keeping with their philosophy of helping students who might be blinded by the light emanating from the Feynman or Landau-Lifshitz volumes, or awed by the sweep and erudition of Jackson. Naturally, they have had to narrow the scope, and must have had to leave out many tempting topics with regret.
The authors have found a novel answer to the vexed question of units. Most equations have a bracketed term whose omission gives the gaussian formula, and inclusion the SI formula - a worthwhile goal achieved at the price of few extra $4 \pi's$ in numerator and denominator. An appendix further clarifies matters relating to units and I found it less cryptic, if more prosaic, than Jackson's.
One strong positive feature is the detailed, ground-up introduction to vector calculus and special relativity. In fact, a general feature is that intermediate steps are not swept under the carpet. A very good example is the derivation of the fields due to an arbitrarily moving charge, by painful differentiation of the Lienard Wiechert potentials. Feynman presents the final result, in a novel form, like the magician he surely is, pulling it out of a (large sized ) hat. Landau-Lifshitz, operating at a comparable hat size, and Jackson, do give the reader some hints, but Capri and Panat ensure that the reader reaches the destination without mishap.
The inevitable narrowness in the choice of material is compensated by the wide range of applications, both in the text and in the problems. Some examples are from accelerator physics (magnets in synchrotrons, waveguides in linacs). A student inclined towards radio astronomy would encounter dipoles of all lengths down worked out to the last ohm of radiation resistance, real resonant cavities with finite Q, an intuitive account of synchrotron radiation, and even the Crab nebula in a problem. The treatment of dielectric and magnetic response goes some distance into condensed matter and atomic physics, so that the student has at least a simplified model of what the microscopic electric and magnetic dipoles contributing to the macroscopic and are. Unusually for a modern book, magnetic pole density and magnetic scalar potential are not treated as untouchables. Of course, statutory warnings about their limitations are included as well.
Personal and informal touches of the kind good teachers use in their classrooms are not lacking - I was struck by the remark that the negative sign in Lenz's law saves us from an exponential blowup of energy! A balance is struck between formal mathematical derivations (as in the chapter on electrostatic boundary value problems) and physical arguments with order of magnitude estimates - surely a rounded physicist needs both.
No review is complete without a list of "cribs", no doubt reviewer dependent, if only to prove that the reviewer really read the book! Mine pertain to a rather small fraction but here they are. On the matter of typos in general, very few of us can afford to cast the first stone. But I still feel printers/proofreaders devils must have worked overtime in the account of Faraday's experiments on dielectrics in capacitors on pages132 and 133. I was also surprised by the three orders of magnitude discrepancy on page 442 between the transition probability quoted for n=6 to n=5 in hydrogen, and the correspondence principle result. I strongly suspect that one pertains to l=1 to 0, i.e to highly elliptic orbits,while the second is for circular orbits and a fairer comparision (i.e with l=5 to 4) would give a smaller discrepancy. And I looked in vain for the Maxwell stress tensor - something which helps intuitive grasp and goes back to the roots of the subject in Faraday's lines of force. And at the risk of being petty, I would also argue that Stokes does not need an apostrophe before the last letter of his name.
But let me not end with complaints. The fact is that electrodynamics is both a vital subject and one not easy to teach, even with (or because of) the classic works on the subject looming large over us. This book will find its niche among serious students and serious teachers prepared to work towards the goal of mastering electrodynamics, and equip them with the skills needed to read the canonical works with appreciation. They will be led firmly by the hand and rewarded by reaching heights with a view. The authors have trusted their personal experience and vision to bring out this text in the face of so many already extant. I am sure their own love for the subject must have seen them through the long and difficult process of writing a new book. The destination (of love) is the same while the travellers change, or, in the orginal Hindi which I am sure some older readers and at least one author will recognise " Manzil wohi hai pyar ka,rahi badal gaye".
Rajaram Nityananda, Director of the National Centre of Radio Astronomy (NCRA)