谁可以帮做道英文物理题

题目

谁可以帮做道英文物理题
Unpolarised white light is shone onto two polaroid sheets lying one on top of the other.
Their transmission axes are at right angles to one another so that no light is transmitted.
A third polaroid sheet is placed in between them and is at an angle of 55 degrees to the bottom polaroid sheet.
Assuming all the polaroid sheets are ideal,what percentage of the incident light will be transmitted?

答案

大概就说两个偏振片加在一起,它们的透射方向已调垂直所以用非偏振光照射后无光通过（消光）；然后再在其中插入第三块偏振片,其透射方向与底部这块偏振片的投射方向成55度,显然用马吕斯定理I'=I*COS^(i）很快能求出,即I'=0.5*cos^（35度）*cos^(55度）*I,结果自己算哈,呵呵