A Bengali pioneer of science

Marking the 150th anniversary of J.C. Bose

The son of a deputy magistrate, Bose was born in Mymensingh, a district in the part of India’s Bengal province that is now Bangladesh. After graduating from St Xavier’s College in Calcutta, Bose pursued his studies in the United Kingdom, first at London University and then at Cambridge University. He received science degrees from both institutions in 1884. Bose then became Professor of Physics at Presidency College — a founding institution of Calcutta University. It had no modern laboratory. Nevertheless, over the next decade Bose carried out ground-breaking investigations into radio, microwave technology and the use of semiconductors.

The 150th anniversary of the birth of an eminent scientist and pioneer of radio will be marked on 30 November 2008. He was Jagadish Chandra Bose (1858–1937).

Dramatic demonstration

In 1895, in the town hall of Calcutta (now Kolkata), India, Bose showed how electromagnetic waves can be sent wirelessly through not only air, but also walls and even people’s bodies. At a public meeting presided over by the Lieutenant Governor of Bengal Sir Alexander Mackenzie, Bose transmitted a wireless signal from a lecture hall through three intervening walls — and Mackenzie — to a room where it rang a bell and ignited some gunpowder.

It was the year before Alexander S. Popov transmitted radio waves between buildings at St Petersburg University in Russia, and two years before Guglielmo Marconi demonstrated radio signalling to officials of the United Kingdom government.

Microwave marvel

A pioneering feature of Bose’s work was that it used ultra-high frequency (up to 60 GHz), millimetre waves of between 5 mm and 25 mm in wavelength. To carry out his studies, he devised novel equipment such as waveguides, horn antennas and polarizers. Improvising with local materials, Bose constructed one of his polarizers from Bradshaw’s Railway Timetable with sheets of tinfoil interleaved in the book’s pages.

Bose’s first paper, published in May 1895, covered the polarization of electric waves by double refraction, and it was the optical qualities of microwaves that interested him, rather than the wireless signalling potential of longer wavelengths. Other researchers did concentrate on this part of the spectrum, and microwaves were not to be studied seriously again for decades.

In 1897, Bose was invited by Lord Rayleigh (who had been one of his teachers at Cambridge) to lecture on his experiments at the Royal Institution in London. He demonstrated his work successfully, and — again ahead of his time — speculated on the existence of electromagnetic radiation from the sun, which was not discovered until 1942.

A better coherer

A year earlier, in 1896 Bose had followed up his demonstration in the town hall by sending a radio signal between two colleges in Calcutta University — a distance of nearly 5 kms. To detect the signal he used one of his inventions: “a mercury coherer with a telephone detector”.

At this period, radio waves were detected with a “coherer”, invented in about 1890 by the Frenchman Edouard Branly (1844–1940). It worked because radio-frequency alternating current decreases the resistance of loose metal filings placed between two electrodes in a glass tube — causing them to clump together, or cohere. They had to be shaken loose again before another signal could be detected.

Bose produced a new coherer consisting of a metal cup containing mercury that was covered in a very thin insulating film of oil. Suspended above was an iron disc that touched the film of oil without breaking it. The film was broken, however, in the presence of a radio signal, so allowing an electrical current to pass through the device and operate a telephone receiver. The system restored itself automatically.

Bose announced the development in a paper presented to the Royal Society in London in 1899. Exactly the same principle was used by Marconi to receive the first transatlantic wireless signal in 1901, but he said that he had received the design from an Italian colleague.

The first patented semiconductor

Bose’s coherer was actually a semiconductor diode, and his work in this field led to the world’s first patent on solid-state diode detectors, granted in the United States in March 1904. It was for the “galena detector”, which Bose developed between 1894 and 1898 and demonstrated at the Royal Institution in London in 1900.

While studying the optical properties of electromagnetic waves, Bose discovered that polarizing crystals have selective conductivity. One of these crystals was galena, the mineral form of lead sulfide. Bose made a pair of point contacts from galena and linked them in series with a voltage source and a galvanometer. As he said in his patent, he had made “a coherer or detector of electrical disturbances, Hertzian waves, light waves or other radiations”. Bose called his device “a universal radiometer,” one of whose uses could be to detect “signals in wireless or other telegraphy”.

Writing about the “History of semiconductor research” in 1955, the co-inventor of the transistor Walter H. Brattain acknowledged Bose’s priority in using a semiconducting crystal to detect radio waves. And according to Sir Nevill Mott, a British physicist who won a Nobel Prize in 1977 for his work in solid state electronics, “J.C. Bose was at least sixty years ahead of his time”.

As well as contributions to physics, Bose made important discoveries in plant physiology (see box). He was also the founder of India’s first facility for modern scientific work: the Bose Research Institute, opened in Calcutta in 1917. It included a large lecture theatre whose purpose, he said, was to disseminate knowledge of scientific advances to the widest possible public “without any academic limitations, henceforth to all races and languages, to both men and women alike, and for all time coming.”

Also in 1917 Bose was knighted, and in 1920 he was the first Indian scientist to become a Fellow of the Royal Society. He left a lasting legacy for science in Asia — and the world.