Which of the following obstacles can be used to block all the gamma radiation?
A. Paper
B. 1mm aluminium sheet
C. 25mm lead sheet
D. None of the above
ans : B
點解答案係B??唔係D咩?
please help!!
thanks!!!
更新1:
physics8801 : 我都係咁諗呀!咁係咪個ans錯呢?? thank you