更新1:
why for 1st order fringe?
更新2:
but for small angle (theta), sin(theta) = tan(theta) = 0.3/2
更新3:
why[but for small angle (theta), sin(theta) = tan(theta) = 0.3/2]?
phy- diffraction
2011-02-19 5:30 pm
When a source of monochromatic light of wavelength 6x10^-7 m is viewed 2 m away through a diffraction grating, two similar lamps are ‘seen’ one on each side of it. Each is 0.3 m away from it. Calculate the number of lines in the grating.
回答 (2)
2011-02-19 6:30 pm
✔ 最佳答案
Using the grating equation for bright fringesa.sin(theta) = m入
where a is the grating line spacing
(theta) is the angular position of a bright fringe of order m
入 is the wavelength of light used.
hence, sin(theta) = 6 x 10^-7/a for 1st order fringe
but for small angle (theta), sin(theta) = tan(theta) = 0.3/2
i.e. 0.3/2 = 6x 10^-7/a
a = 4x10^-6 m
Hence, no. of lines in the grating = 1/a = 1/4x10^-6 lines/m =2.5x10^5 lines/m
2011-02-19 7:32 pm
收錄日期: 2021-04-20 00:09:14
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110219000051KK00243