half value thickness

例句：

1. 1. The material has a half value thickness of 0.5 mm.
   这种材料的半值厚度为0.5毫米。
2. 2. The thickness of the wall is half value to the length of the room.
   墙的厚度是房间长度的一半。
3. 3. The thickness of the material is determined by its half value thickness.
   材料厚度由其半值厚度决定。