Mitra started post-graduate teaching and research activities on radio science for the first time in India. He established an independent postgraduate department of electronics and radio physics in Calcutta University in 1947 that later evolved into the Institute of Radio Physics and Electronics. He established the first ionospheric field station in India. It was Mitra, who felt the need for an all India radio research organisation and the Radio Research Committee was formed by the Government of India in 1942 under Mitra’s chairmanship. Mitra’s concern for industrial development is well-known, and he initiated industrial projects in his laboratory.
Sisir Kumar Mitra was born on 24 October 1890 in Kolkata. His father JoykrishnaMitra was a schoolteacher. At the time of Sisir Kumar Mitra’s birth, his mother Saratkumari was a student of Campbell Medical School (later renamed as Nil RatanSarkar Medical College) in Kolkata. After passing the final examination in 1892, Saratkumari got an appointment in Lady Dufferin Medical Hospital in Bhagalpore (now usually written as Bhagalpur) in Bihar (now in Jharkhand) and the whole family moved there. His father also managed to get an appointment as a clerk in the local municipal office. Joykrishna had married Saratkumari against the wishes of his parents and because of this he was not only disinherited from his parental property, he was also banished from home.
Mitra studied at the BhagalporeZilla (District) School. He then proceeded to the T.N.J. College, Bhagalpore to clear the FA Examination. Just before he passed his FA examination, he lost his father. In 1908, he joined the Presidency College, Kolkata as a BSc student, where he came under the influence of Jagadis Chandra Bose and Prafulla Chandra Ray, two pioneers of modern scientific research in India. At the Presidency College, he was fascinated by instruments designed and constructed by J.C. Bose used to study properties of microwaves and detect various responses of plants. In 1912, Mitra secured his MSc degree in physics as a topper.
The stalwarts referred above inspired him to dedicate himself to scientific research. He got an opportunity to work under J.C. Bose soon after he cleared his examinations. Importantly it was not easy to get a research fellowship those days. His widowed mother supported his education in Kolkata and them as a family needed financial help. Her income was not sufficient at this stage of his career. So when Mitra got an appointment as a lecturer in the T.N.J. College at Bhagalpore, he left Kolkata to take it up. From Bhagalpore he moved to Bankura in West Bengal on securing a job as a lecturer at the local Christian College.
While teaching in colleges, Mitra continued to harbour a burning desire to pursue a research career. However, there was no scope for carrying out research in these mufassil colleges. Mitra tried to use his time as best as he could. He devised indigenous demonstration experiments with whatever he could collect from the impoverished college laboratory to make his lectures more enjoyable and instructive. He wrote popular science articles in Bengali.
Mitra could finally realize his dream of carrying out research when AsutoshMookerjee, the then Vice-Chancellor of Calcutta University, invited him to join the newly created Physics Department of the University College of Science. Mitra worked under Raman’s guidance on interference and diffraction of light for his doctoral thesis, in the latter’s laboratory at the Indian Association for the Cultivation of Science. His doctoral thesis earned him a DSc degree from Calcutta University in 1919.
In 1920, Mitra proceeded to the University of Sorbonne in Paris to join the research group of Charles Fabry (1867-1945), who had discovered ozone in the upper atmosphere in 1913. At Fabry’s laboratory Mitra worked on determining the wavelength standards (2000-2300 Angstrom of the copper spectrum). This fetched his second doctorate in 1923. He then got the chance to work under Marie Curie. He then went ahead to the Institute of Physics at the University of Nancy, Paris, where he worked on radio valve circuits. Though he spent only a few months at the Institute of Physics, he finally made up his mind to make his career in radio research. It was a bold decision because in those days radio science in India was still in its infancy. Radio science was not a part of the curriculum in any university in India. A research facility in this subject was just not available. Mitra was not deterred and wrote to Asutosh Mookerjee about his decision to move to India. Mookerjee in his reply dated 10 May 1923 wrote: “I am glad to receive your letter dated 18th April and to hear that you have been so successful in your work. The course of investigation you suggest as to signals by wireless telegraphy is very attractive. Do please draw up a scheme and make it as inexpensive as possible. I shall see what we can do. But you must rest assured that there will be plenty of opposition. That need not frighten us; we shall have to fight our way through.” On his return to India, he was appointed Khaira Professor of Physics.
He became a member of a team that had C.V. Raman, D.M. Bose, and others. They organised post-graduate teaching in physics at the Calcutta University. Mitra established the ‘wireless section’ and launched into postgraduate teaching and research in this area. He could motivate a small team of young and enthusiastic individuals to take up the challenging task of studying the ionosphere, which plays a major role in long-distance radio communications.
Mitra and his group measured the heights of different layers of the ionosphere using an instrument designed and built indigenously. These investigations provided the first overview of the ionospheric condition in a low altitude sub-tropical region. This also threw considerable light on the effect of thunderstorm, magnetic storm and meteoric shower on upper atmospheric ionisation. Mitra and his co-workers conclusively established the existence of the D-layer.
While developing teaching and research facilities in radio science at Calcutta University, Mitra was involved in the development of broadcasting in India. He and his co-workers constructed a transmitter and installed it in the newly established Wireless Laboratory at the University College of Science. Interestingly for quite some time Mitra’s transmitter in his Wireless Laboratory and the transmitter of the Radio Club of Bengal at Dalhousie Square were the only ones that broadcast programmes in the Eastern region of India regularly.
Prof. J.N. Bhar, a student of Sisir Kumar Mitra in his memoir, narrates the unique communication ability of Prof.Mitra. “While delivering lectures in the post-graduate classes of the University or scientific conferences or outside, addressing a much less sophisticated audience on popular or semi-popular topics, Prof.Mitra appeared to be equally at ease. What marked his talks as outstanding was his clarity of exposition. There was a complete absence of superfluity in his talks, yet nothing was left unsaid. Every word seemed to have been chosen with care. Every sentence that he uttered was meaningful.”
Mitra established a field station for ionospheric work at Haringhata, a village about 50 km from Kolkata in 1949 with financial assistance provided by the Council of Scientific and Industrial Research (CSIR). This was the first ionosphere field station of its kind in India. Mitra was appointed as Emeritus Professor by Calcutta University after his retirement in 1955. After his retirement, he was persuaded by the then Chief Minister of West Bengal to head the State’s Board of Secondary Education. When he took over, the Board was in bad shape. HE transformed the Board into an efficient institution within a short span of time. He received many awards for his significant scientific contributions. In 1958, he was elected Fellow of the Royal Society of London for his contribution to the study of upper atmospheric phenomena. In 1963, he was appointed as National Research Professor by the Government of India. He planned to utilise this opportunity for preparing a revised third edition of his acclaimed treatise The Upper Atmosphere. This remained an unfulfilled dream on account of his demise.