摘要或動機

雷射光碟（以下簡稱ＣＤ）除了在電腦、音響方面有甚佳的視聽功能外，在光線照射下，呈現彩虹狀的光譜，必定引起你我研究其光學性質的興趣。國內以ＣＤ研究光的繞射的著作，有李偉等四人近三年發表五篇，國外科教期刊自1991年迄今共有19 篇，在老師指導下，利用ＣＤ進行了8 項實驗，分成三大項。1.利用氦氖雷射分別照射舊唱片、ＣＤ、ＤＶＤ，反射光形成繞射現象，由dsinθ=mλ，量出槽距。2.將ＣＤ-R 的鋁層刮掉，（整疊購買的ＣＤ-Ｒ上下有數片未鍍鋁的瑕疵片），成為透光式ＣＤ（透射式光柵），將其中心半徑5.5 公分部份，用黑紙遮住，正對陽光，螺旋狀的溝槽將陽光聚成一點，量出各色光到ＣＤ的距離，可算出色光的波長。3.透射式ＣＤ置於投影機鏡頭前方，投影機置物台上，放置化學藥品，可直接在屏上觀察吸收光譜。The rainbow of colors reflected from the surface of an audio compact disc (CD) is a familiar sight.It is the phenomenon of light diffraction. A standard CD has 20,625 turns of the spiral, and each line is spaced by 1.6μm. This provides a grating of 625 lines/mm. We used ordinary CDs as reflection grating in our experiment,and transparent factory rejects with no coating but printed data spirals as diffraction grating. We conducted eight experiments of diffraction using the two kinds of CD. (a) Determined the grating spacing of an ordinary CD using a laser beam. (b) Determined the grating spacing of a transparent CD using a laser beam. (c) Studied the diffraction patterns caused by a laser beam held at angles to a transparent CD. (d) Measured the wavelengths of sunlight using a transparent CD. (e) Measured the wavelengths of sunlight using an ordinary CD. (f) Formed a rainbow using a transparent CD. (g) Observed the scattering of light using a transparent CD. (h) Demonstrated the absorption spectrum using a transparent CD and an overhead projector.