Proceedings of the Indian Academy of Sciences - Section A

Raman, C.

doi: 10.1007/BF03047057pmid: N/A

Raman, C.

doi: 10.1007/BF03047058pmid: N/A

Rajagopalan, S.; Ramaseshan, S.

doi: 10.1007/BF03047059pmid: N/A

An elliptic analyser, consisting of a birefringent element and a linear element, can be converted into a rotating elliptic analyser by rotating one or both the elements. The Poincaré sphere could be scanned, with such a device, along a meridian, a latitude circle, a great circle of any arbitrary inclination to the equator or any oblique path. Continuous analysis of polarised light can be accomplished by using such an analyser. The principles of some of the possible methods of analysis are presented. The problem of analysis of partially polarised light is also briefly discussed. The speed of analysis is important in analysing changing states of polarisation and depends on the speed of rotation of the elliptic analyser. It is pointed out here that fast rates of scanning are possible by using an electro-optic cell as a birefringent element and rotating the field that causes birefringence.

Ramana Rao, S.

doi: 10.1007/BF03047060pmid: N/A

The author demonstrates, using group-theoretical method, that in any point group G, to each such subgroupg of indexf as can repeat a motif crystal face in itself, and to all its conjugate subgroups in G, corresponds anf-faced crystal form (open or closed). If subgroupg is self-conjugate, the form corresponds to it alone.

Manohar, H.; Ramaseshan, S.

doi: 10.1007/BF03047061pmid: N/A

A systematic study has been made of the crystal co-ordination of the barium ion in various compounds whose structures have been solved. Apart from the more common co-ordination polyhedra which are enumerated in text-books, a number of new polyhedra have been identified, particularly in cases where the co-ordination numbers are unusual, such as ten or eleven. According to the radius-ratio rule of Pauling, a co-ordination number of nine or ten is normally expected for the barium ion. The present investigations, however, reveal that it shows a variety of co-ordinations with ligancies from six up to twelve. Some of the factors that might possibly enter in explaining this wide range of co-ordination numbers are discussed. It appears as though the part played by the Ba2+ ion in deciding the structure is secondary, limiting itself only to occupying vacant spaces provided by other atoms in the crystal.

Kotadia, K.

doi: 10.1007/BF03047062pmid: N/A

In this paper, the ionospheric data of Kodaikanal (magnetic dip 3·5° N) have been examined to study the relation between the critical frequency of the equatorial sporadic E layer and the horizontal component of the earth’s magnotic field, with special reference to the behaviour of the electrojet both under normal and under disturbed conditions. Some specific SC type magnetic storms have been analysed to study the effect of the storms on the electrojet.