Problem of contribution functions and the calculation of average optical depths of formation of Fraunhofer lines

The functions of contribution to emission and depression and the so-called response functions are considered. On the basis of the physical conditions existing in the solar atmosphere, an attempt is made to formulate the demands imposed on the contribution functions used to calculate the average optical depths of formation of Fraunhofer lines. The average optical depths of formation of various sections of certain Fe I and O I Fraunhofer lines are calculated as an example