73.兩個半值層(half value layer, HVL)再加上兩個十一值層(tenth value layer, TVL)的屏蔽,可使原來的窄
射束光子輻射強度衰減成幾分之幾?
(A)1/100
(B)1/200
(C)1/400
(D)1/800
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統計: A(38), B(88), C(2966), D(67), E(0) #1943893
統計: A(38), B(88), C(2966), D(67), E(0) #1943893