1、2. Diffusion cloud chamber擴散雲室 a. enable tracks of radiation to be seen.顯示輻射軌跡b. alcohol vapour condenses around the ions, under strong illumination, it reflects light & is revealed as white tracks in a dark background. （ In general, one track corresponds to one charged particle ） 酒精分子凝結在輻射造成的離子上，每條
2、軌跡代表一粒輻射c. dRadiationTracks路徑Explanation原因1.2.3.strongest ionization power強電離能力easily deflected by the air molecules質量輕, 容易被偏轉。3. Spark counter火花計數器high ionizing power radiation高電離能力 will produce lots of sparks, e.g. particles, & sources hardly produce any sparks. 的高電離能力令電極間產生火花， 和 則難以產生。4. GeigerMu
3、ller Tube （GM tube）蓋革彌勒管. suitable for detecting all three kinds of radiation.適合量度各種輻射27.2 Types of Nuclear Radiation各種輻射Ionizing ability電離能力（An outer shell electron is knocked out from the atom, creating an ion pair原子的外圍電子被輻射線撞開，成為離子偶）Ionizing power電離能力： Penetrating power穿透能力 射線被 radiation is stopp
4、ed by .隔絕 射線被 radiation is stopped by . 隔絕 射線被 rays is never . 隔絕 Penetrating power穿透能力：Deflection in magnetic field磁場偏轉Alpha, beta & gamma radiationProperty radiation radiation radiation Nature性質SymbolCharge電荷Speed速度up to speed of lightspeed of lightSource來源Americium鍎 （Am-241） Strontium鍶 （Sr-90）Cob
5、alt鈷 （Co-60）Effect of electric fields電場影響Effect of magnetic fields磁場影響Detectors測量器4.Use Flemings left hand rule弗林明左手定則。畫出 , 及 的 路徑1998 HKCEE Q40.1 兩帶電金屬板產生一勻電場 . 下列哪個圖形顯示 ,和射線在該電場中的偏轉 ?1997 HKCEE Q392. 下列哪一項有關粒子敘述是不正確的 ? A . 粒子不能穿過一張紙 . B . 粒子受磁場偏轉 . C . 粒子可使照相軟片感光 . D . 粒子可以通過真空 . E . 粒子是由高速移動的電子組成
6、 .1999 HKCEE Q383. 下列各項關於粒子的敘述 , 哪一項不正確 ? A . 粒子不能穿過一張紙。 B . 粒子可使照相軟片感光。 C . 粒子受磁場偏轉。 D . 粒子在空氣中的射程只有數量米。 E . 粒子不能通過真空。Although the nature of each radiation was uncovered揭露, the cause原因 of radioactivity was only satisfactorily explained after the discovery發現 of neutrons中子 & protons質子 inside the atom
7、s.Right-angled fork tracks直角分叉徑跡It shows that radiation is .27.3 Radiation Hazards輻射的危險 Hazards1. Radiation can destroy or damage living cells. 損害細胞2. The radiation can change DNA and RNA which control how the cell works破壞脫氧核糖核酸.3. It may lead to cancer or incurable radiation sickness.導至癌症Safety pre
8、cautions安全措施1. Store & transport in a suitable lead container儲存在鉛箱內.2. Always lifted with forceps使用鉗子.3. The open window must be directed away from the body不可指向任何人.4. Never brought close to the eyes for inspection不可用眼睛檢射線被查.5. All storage places should be marked with a warning sign. 儲存地點加上警告標誌Backgr
9、ound radiation本底輻射1. Evidence證據 Without the presence存在 of a radioactive source, a GM counter still counts continuously. 即使沒有放射源，GM計數器亦有讀數，這是因為本底輻射。2. Sources來源 a. d.b. e.c.Radiation dose輻射劑量1. most susceptible易受影嚮 parts of human body to radiation: i. reproductive system生殖系統 ii. immune system免疫系統 iii
10、. eyes眼睛2. Result of over-dose of radiation: 1. Somatic肢體 effect - damage of whole organs due to extra high dosage. 2. Cancer 癌症 3. Genetic effects 遺傳- damage of genes & affects the next generations 4. Death 死亡- dosage over 5000 mSv.3. Another danger of radiation is that it is accumulative積聚.2000 HK
11、CEE Paper I Q66. 為了找出某放射源放出哪些輻射，現將一個蓋革-彌勒計數器靠近該放射源。在放射源和計數器之間輪流放入不同的吸收體，每次均利用計數器錄取三個讀數，每個讀數歷時一分鐘，所得結果如下:吸收體計數器錄得的讀數/每分鐘次數第一次讀數第二次讀數第三次讀數-700710693紙板7027037011 mm 鋁板3133203175 mm 鉛板98101100表 1 計數器量度到的本底計數率為每分鐘 100 次.（a） 對於每一種吸收體，計數器錄得的三個讀數都不相同，試加以解釋。（1 分） *（b） 解釋以上結果如何證實該放射源只放出幅射而沒有放出和輻射。（5 分）Chapter 28: Radioactivity II 放射現象28.1 The Nuclear Atom原子1. 1803 John Dalton Matter is composed of tiny particles called atoms.物質由原子組成2. 1895 Discovery of electron發現電子.3. 1898 J. J. Thomson Plum pudding.4. 1900 Atoms are made up of smaller particles. 原子由粒子組成5. 1909 Rutherford New model of atom創立
