Colloquium

Revisiting diffraction

Speaker: Rajaram Nityananda (Azim Premji University, Bengaluru)

Date and time

Abstract

Our understanding of the way telescopes function is customarily based on a picture of diffraction going back to Fresnel (with Huygens name also attached), summing up waves originating from all points of an aperture.   It has long, but perhaps not widely, been known that this picture is fundamentally flawed, in spite of its qualitative and quantitative successes in its range of validity - apertures many wavelengths in size, implying small solid angles. Low frequency radio astronomy, and in particular experiments on the epoch of reionisation, has forced a deeper examination of how telescopes function.  This talk will begin with the conceptual aspects of diffraction, and then highlight some aspects relating to radio telescopes in current use.

Prof. Rajaram Nityananda

Short Biography
Rajaram Nityananda studied physics at the Vivekananda College and Indian Institute of Technology, in Chennai, and later worked for the PhD degree of the Bangalore University, in the areas of optics and crystallography at the National Aerospace Laboratory. After joining the Raman Research Institute, in Bangalore in 1975, he worked mainly on theoretical aspects of astronomy, such as image processing, gravitational lensing, and gravitational dynamics. In the year 2000, he moved to Pune, as the Centre Director of the National Centre for Radio Astrophysics of the Tata Institute of fundamental Research. He retired in 2013, and since then has taught physics to undergraduate students, first at the IISER in Pune and for the last seven years at Azim Premji University, in Bangalore. He is a fellow of the three science academies in India, and has served as editor of the physics and astronomy journals of the Indian Academy of Sciences. From 2014 to 2017, he was the Chief Editor of Resonance, the journal of Science Education and has also written many articles on topics in physics and astronomy for that journal.