30.當偵檢器的直徑為8公分,離一點射源20公分,試問該幾何效率(geometric efficiency)為何?
(A)1%
(B)5%
(C)10%
(D)50%
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統計: A(488), B(462), C(530), D(166), E(0) #1384333
統計: A(488), B(462), C(530), D(166), E(0) #1384333