醫療類國考
112年
[醫事放射師] 醫學物理學與輻射安全
第 74 題
通常純貝他射源使用低原子序之材質作為輻射防護之內包裝屏蔽的原因為何？
- A 比較輕巧方便
- B 電子的射程很短
- C 產生較少的擾動
- D 減少產生制動輻射
思路引導 VIP
當高速電子（貝他粒子）進入物質並受到原子核庫倫電場作用而減速時，其動能轉換為高穿透性光子的「制動輻射」（Bremsstrahlung）發生機率與屏蔽材質的原子序 $Z$ 有何比例關係？若要將這種二次輻射的產生率降至最低，內層屏蔽材質的原子序應該如何選擇？
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AI 詳解
AI 專屬家教
(No title, just strictness)
- Barely Acceptable: Oh, look at that. You actually managed to identify the fundamental principle of matter-radiation interaction. Remarkable. One might even say it's a basic requirement for anyone attempting to work in this field.
- Basic Validation: Apparently, you've stumbled upon the concept that when beta particles (electrons) slow down near an atomic nucleus, they release their kinetic energy as photons. We call this 制動輻射 (Bremsstrahlung). The obvious relationship is that its production is proportional to the shielding material's atomic number $Z$:
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