十分PHY-wave

用戶19890

2007-10-07 6:10 am

關於 2-slit interference pattern of light
If one slit is covered by a glass slide, the central maximum would shift towards the side of covered slit.
μ : refractive index of the glass, t: thickness of the glass
1) optical path= 入/入' x t = 入/(入/μ)x t=μt
甚麼是optical path? 甚麼是 path
點解個optical path是用這個方法黎搵?
optical path difference
Δ=μt-t
點解個path difference用這個方法黎搵?

回答 (1)

天同

2007-10-07 9:48 am

✔ 最佳答案

It is because light wave travels slower in a medium. Optical path is [the length within which (the medium) contained the same number of wavelengths of the light wave as it is in air (or vacuum).]
Let 入 be the wavelength of light in air, and 入' be the wavelength of light in the medium,
since refractive index μ = c/v = f入/f入' = 入/入'
i.e. 入' = 入/μ
where c and v are the velocities of light in air and in the medium respectively and f is the frequency of light, which is the same in both air and the medium.
Let the length of the medium = t
hence, no. of wavelength contained in length t of the medium = t/入' = μt/入
The length of air that should contain the same number of wavelengths
= [μt/入].入 = μt
which is the optical path
Therefore, optical path, physically, means the length t of a medium with refractive index μ, is equivalent to a length of μt of air.

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