天同師兄,有關果條inter vs diffraction

2011-03-28 6:41 pm

有關你回答果條
http://hk.knowledge.yahoo.com/question/question?qid=7011032700146

你話In the actual fact, this assumption is made because the slits must behave like two coherent "point sources" (a point source has no dimension, in theory).

想請問咩叫a point source has no dimension?

仲有唔該答答呢呢條丫,唔該!
http://hk.knowledge.yahoo.com/question/question?qid=7011032700649

更新1:

同埋你果個animation呢,個wavelength 既order係10^-9 and slit widht 係10^-3,但係點解你會話slit width to as small as you could (down to 0.1 micrometer). When it is much smaller than the wavelength (550 micrometer), 同埋如果係咁,個slit width 最細都大佢幾十-百倍喎,點解會咁?

更新2:

SORRY,order果度我錯左,唔好意思

回答 (1)

天同

2011-03-29 5:12 am

✔ 最佳答案

Originally, the interference pattern is formed, in theory, by placing two coherent and monochromatic point sources, separated by a short distance. As you know that, in geometry, a "point" has no dimension (i.e. no length, breadth and height). In reality, point sources could not be found, Hence, these point sources are replaced by narrow slits. The narrower the slit, the closer it is to the performance of a point source. If the width of the slit was wide, then there would interference of light coming from different part of the slit width itself.

Sorry that I have mistyped the wavelength, it should be 550 nanometer, i.e. 0.55 micrometer. If the slit width of the animation is set at 0.1 micrometer. The wavelength is about 5 times larger than the slit width. The slit could be regarded as "point source".

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