91av

THE STORY began in 1666 when Isaac Newton shone a thin beam of sunlight through a triangular glass prism. As the light emerged, it fanned out into the familiar rainbow spectrum of colours, from red to violet. When the German optician Joseph von Fraunhofer repeated this famous experiment in 1814, he produced a much sharper spectrum by first filtering the sunlight through a narrow slit before it reached the prism. On closer inspection, Fraunhofer noticed that the spectrum was crossed with hundreds of dark lines (later called Fraunhofer lines) corresponding to specific colours or frequencies of light missing from the…