The Relation with Light Wavelength

The first topic concerns the two laws of photochemistry that correspond to the following (or similar) statements  

Only light which is absorbed by a system can cause chemical change (first law, 

For every quantum of light that is absorbed, one molecule of substrate reacts 

Let us consider a photochemical experiment as it was carried out by the baron Theodor Grotthuss, then living in his native Courland, a part of modem day Latvia [3-5] (Fig. 2.1). 

Beobaebtugei, die Lbsug des salssanreo Eisenexydes in Alkohol betreffeod. 

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