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如图所示为某种材料做成的透明光学器件,横截面\(AB\)为半径为\(R\)的四分之一圆弧,\(O\)为圆心\(.\)一束宽度为\(R\)的单色平行光垂直\(AO\)面入射,该器件对光的折射率为\(n= \sqrt {3}.\)点\(C\)、\(D\)位于\(AO\)表面上\(.CO= \dfrac {R}{2}\),从\(C\)点入射的光线从\(AB\)弧面上的\(E\)点射出,出射角为\(β.\)从\(D\)点入射的光经\(AB\)弧面一次反射后直接到达\(B\)点\(.\)求:
\((\)Ⅰ\()β\)的大小;
\((\)Ⅱ\()\)通过计算说明从\(D\)点入射的光能否在\(AB\)弧面发生全反射?