This paper studied the propagating process of light in a uniaxial birefringent and a faraday rotatory plane parallel plate under nearly normal incidence. Due to birefringence

a beam of polarized light splits into two beams (one ordinary and the other extraordinary). The planes of polarization of the two refracted beams will rotate a certain angle because of faraday rotatory effect. When they go into birefringent plate again

the number of the beams will be doubled. The light is reflected and refracted many times in these two plates. The number of beams is increasing in geometric series and multiple beams interference is produce.