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316 : Scientific Contents in Prākrta Canons
It seems that mirrors were known during Akalanka days of eighth century A. D. The scholars could see the laterally inverted images in mirrors. The cause of this inversion is said to be the nature of reflecting surfaces. However, its main cause is the linear propagation of light. This is indicative of the fact that this phenomenon was unknown during those days. There is full knowledge about the virtual image formation now and mathematical relationships have been developed for the shape and size of the image at the reflecting surfaces. There are many toys for the children made on this basis. The canonical language indicates that the first type of shadows are equivalent to virtual images as seen in mirrors.
The second type of real and/or inverted images are called only images in literature. But there are no examples of these images. This might be due to the fact that there may not be knowledge of different types of lenses. However, even the foresight of these types of images seems to be a good gesture about the scholars' keen intellectual insight. Now-adays, magic bouquet and daggers are played with the help of lenses.
The images formed by different reflecting surfaces are given in figures below. The normal shadow can be exemplified by solar eclipse. It is seen that when moon comes in between earth and sun, there is solar eclipse ( fig. 1). If the reflecting surface is plane, the image is formed at the same distance behind as the object from the surface. If it is a convex or concave surface, the situation becomes different. With the convex mirror, the image is virtual ( fig. 2) while with the concave mirror, it is real ( fig. 3).
SUN
Earth
Fig. 1 : Solar Eclipse.
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