Two identical matte plates P1 and P2 form a right dihedral angle. The edge of this angle is placed at equal distances from the light sources S1 and S2 on the straight line connecting the sources (Fig. 144). It turned out that the illumination of both plates is the same when the bisector of the dihedral angle forms an angle a with the perpendicular to the line S2S2. Find the ratio I1/I2 of the light intensities of the sources. Assume that the linear dimensions of the plates are much less than the distance S1S2.

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