Two parallel plane-polarized beams of light of equal intensity whose oscillation planes N1 and N2 form a

Question:

Two parallel plane-polarized beams of light of equal intensity whose oscillation planes N1 and N2 form a small angle ф between them (Fig. 5.30) fall on a Nicol prism. To equalize the intensities of the beams emerging behind the prism, its principal direction N must be aligned along the bisecting line A or B. Find the value of the angle ф at which the rotation of the Nicol prism through a small angle δ ф