單狹縫繞射實驗之研究

單狹縫繞射實驗是物理實驗介紹光的波動性的一個重要實驗。但傳統的實驗中利用雷射經狹縫片後以目測紀錄亮、暗點（建設性干涉、破壞性干涉）而計算出的波長誤差可高達20%以上。此分析為遠場繞射（又稱為Fraunhofer繞射）。對於近場繞射（又稱為Fresnel繞射）之分析，傳統繞射實驗無法觀測得知。本研究以電腦化來分析影響單狹縫繞射的條件。首先、經由改變狹縫片與紙屏（接收器）之距離，來分析出未繞射、近場繞射、遠場繞射之距離關係。以狹縫寬為0.016cm之單狹縫，波長為652.5nm之雷射照射時，分析出距離9cm為近場繞射與遠場繞射之分界。9cm以上之繞射屬遠場繞射，電腦化實驗求出波長誤差可降至10%以下。第二、分析狹縫寬與繞射之關係。當距離固定為為50cm時，以波長為652.5nm雷射照射時，狹縫寬度須在0.02cm以下方可清楚測出遠場繞射。第三，經由分光與混光實驗讓同學了解光的三原色與單頻光為形成單狹縫繞射之主因。

關鍵字

繞射；近場繞射；遠場繞射

並列摘要

The experiment of single-slit diffraction is one of the important physics experiment to introduce the wave optics. Using eye-measurement of tradition method to record the bright and dark point of single-slit diffraction, the experimental results indicate that the wavelength error percentages are over 20%. This analysis is the far-field diffraction (Franhofer diffraction). Another diffraction is near-field diffraction (Fresnel diffraction) which can not be analyzed by eye-measurement method.This research analyses the conditions of influenced the single-slit using the computerization. At first, we change the distance between slit and detector to find out the relation of non-diffraction, near-filed diffraction, and far-field diffraction. For the 0.016 cm-slit width, using He-Ne laser with 652-nm wavelength to pump, the critical distance is 9 cm. If the distance less than the critical distance indicates the near-field diffraction, otherwise, it indicates the far-filed diffraction. Computerization indicates that the wavelength error percentages are less than 10%. Second, we analyze the relations between slit width and the diffraction. For the 50 cm distance, the width of slit must less than 0.02 cm which can be clear to find out the far-field diffraction. Third, the color mixture or separate experiments are good for understanding consists of three primary color. The single-frequency light can successfully structure the far-field diffraction experiment.

並列關鍵字

diffraction ； near-field diffraction ； far-field diffraction

國際替代計量

單狹縫繞射實驗之研究

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