Задача 40990.

The two polarizers are located so that the angle between their planes is 30 °. Determine how many times the intensity of natural light will decrease when passing through both polarizers if a quartz plate is placed between them, rotating the plane of polarization at an angle of 45 °.

Detailed solution with a brief record of the conditions, formulas and laws used in the decision, the conclusion of the calculation formula and the answer.
If you have any questions about the decision, write. I will try to help. File in image format.