The surface region which yields a continuous spectrum is called the photosphere; it possesses optically a sharp boundary, which is generally a perfect sphere, but shows occasionally at the rim slight depressions or more rarely elevations.
Throughout the year, and the atmosphere is both chemically and optically of singular purity.
There are a number of optically bright lines of longer wavelength.
A standard 128 Efork could then be compared either optically or by beats with the electrically driven fork.
The osazone prepared from a-acrose resembled most closely the glucosazone yielded by glucose, mannose, and fructose, but it was optically inactive; also the ketose which it gave after treatment with hydrochloric acid and reduction of the osone was like ordinary fructose except that it was inactive.
The substance is usually optically isotropic, though sometimes it exhibits anomalous double refraction; fibrous zinc sulphide which is doubly refracting is to be referred to the hexagonal FIG.
Their solutions are optically active, i.e.
It is optically active, the natural form being laevorotatory.
This is valid so long as the pencil is in air; but if, on the other hand, the pencil passes from air through a plane surface into an optically denser medium, e.g.
It crystallizes in colourless prisms and is optically active.