In 1938, Indian physicist Bibha Chowdhuri and D.M. Bose exposed samarium-soaked photographic plates at high altitudes in Sandakphu and Darjeeling to detect cosmic radiation and map subatomic nuclear disintegrations. Their experimental emulsion technique recorded 30 star-like tracks left by charged particles, establishing light-sensitive photographic plates as viable detectors of subatomic events.
She isolated cosmic particle trajectories. This methodology directly enabled scientists to differentiate heavy particles, including protons and mesotrons, based on track scattering patterns across varying elevations up to 14,500 feet at Pharijong. However, wartime supply disruptions during the Second World War severed access to specialized Ilford halftone plates from England, halting further cosmic ray experiments at the Bose Institute in Kolkata. While Nobel laureate Cecil Powell subsequently collaborated with Ilford Ltd in Bristol to refine these nuclear emulsions, Chowdhuri's pioneering research provided the essential empirical proof for photographic particle detection techniques.