物理(十二).doc

XI Quantum Physics I Quantum Physics 量子物理的發展是圍繞著兩個主題：一個是原子結構的探索，另一個波與粒子的二重性。 Photoelectric effect and the idea of photon 光電效應是以光照射金屬板，然後研究被激發離開金屬板的光電子： Adjust the  HYPERLINK javascript:top.newWin(keywords,content/index/index37.htm,20,20) potential difference V by moving the sliding contact in the above Figure so that collector C is slightly negative with respect to target T. This  HYPERLINK javascript:top.newWin(keywords,content/index/index37.htm,20,20) potential difference acts to slow down the ejected electrons. We then vary V until it reaches a certain value, called the stopping potential Vstop, at which the reading of meter A has just dropped to zero. When V = Vstop, the most energetic ejected electrons are turned back just before reaching the collector. Then Kmax, the kinetic  HYPERLINK javascript:top.newWin(keywords,content/index/index50.htm,20,20) energy of these most energetic electrons, is (39-4) where e is the elementary  HYPERLINK javascript:top.newWin(keywords,content/index/index34.htm,20,20) charge. Measurements show that for  HYPERLINK javascript:top.newWin(keywords,content/index/index45.htm,20,20) light of a given frequency, Kmax does not depend on the intensity of the light source. 愛因斯坦假設這顯示當光與物質（金屬板）交換能量時，是以粒子的形式，一次只交換一個能量量子（Photon），而光的強度只決定光量子的數目，而一個量子之能量與頻率有關。要決定此關係可以改變光的頻率，重複此一實驗，所得到的結果如下圖所示。這個線性結果顯示光子能量與頻率成正比： Einstein summed up the results of such  HYPERLINK javascript:top.newWin(keywords,content/index/index51.htm,20,20) photoelectric experiments in the equation (39-5) This is a statement of the conservation of energy for a single  HYPERLINK javascript:top.newWin(keywords,content/index/index51.htm,20,20) photon absorption by a target with work function F.  HYPERLINK javascript:top.newWin(keywords,content/index/index50.htm,20,20) Energy equal to the photons energy hf is transferred to a single electron in the material of the target. If the electron is to escape from the target, it must pick up energy at least equa