Spectroscopy in ancient India an application of spectroscopy to astrophysics
Dhvānta Pramāpaka Yantra of Maharṣi Bhardvaja (Spectrometer/Monochromator)1 has been described in Aṃśu Bodhinī with a commentary of Bodhananda received from the library of Oriental institute of Vadodara (Baroda). The study of this text has revealed not only the instrument but the materials also, which were used for prisws and windows in different ranges of radiations. One of these materials, namely, `Prakasa Stambhanabhida Lauha2' -a novel non-hygroscopic material of range 5000 cm-1 to 1400 cm-1 -has also been prepared at National Metallurgical Laboratory, Jamashedpur and few others are under the process of their investigation.
The text of Aṃśu Bodhinī further describes and enumerates various radiations (tama) with their symbolic names and their respective measures expressed in terms of an Ancient appropriate unit of angle kakṣya (1 kakṣya = 10-4 radian) related to their corresponding deviation produced due to the dispersion through the prism. In this paper, probably we are to reproduce the above said data through the theoretical approach to suit the present problem which in turn leads to draw following conclusions, viz., (i) The special vertical design of this spectrometer is to suit the requirement of receiving the stellar radiation., (ii) For the regeneration of the data theoretically one has to assume that in the present case a conical flint glass prism of 300 base-angle with the flat face being normal to the incident collimated beam of stellar radiation was used., (iii) The wavelenghths corresponding to kakṣya data fairly tally with that of the Fraunhoffer's lines right from A to K, covering almost the whole visible range of solar radiation and (iv) The format of symbolic names (sāṇketa) goes parrallel to the modern spectroscopic classification of star types.
Over and above in order to tackle the problem, probably for first time, the sine formula of refractive index is divided into such two parts which are compatible to Cauchy's formula, which may prove easier and useful for experimental determination of wavelengths by a prism spectrograph.
Key words: Ancient spectral classes of stars, Astro- spectrometer, Fraunhoffer lives with ancient symbols, Kakṣya-a new unit of angle, Solar spectra
Indian Journal of History of Science, Vol. 33, no. 3 (1998)