From: kfl@KeithLynch.net   
      
   Henry Spencer  wrote:   
   > To stop X-rays, you basically need mass.  Most any kind of mass   
   > is as good as any other kind; essentially nothing is transparent   
   > to X-rays.   
      
   No.  There's a strong dependency on atomic number.  Lead blocks x-rays   
   much better than the same mass of water does.   
      
   (That's why I was working with beryllium many years ago.  It makes a   
   good airtight x-ray window.)   
   --   
   Keith F. Lynch - kfl@keithlynch.net - http://keithlynch.net/   
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