phy- diffraction

Larry

2011-02-20 4:53 pm

A diffraction grating is illuminated normally by light of wavelength λ1 and λ2 respectively. i) If N1 > N2, what can you say about λ1 and λ2ii) If λ1 > λ2 what can you say about N1 and N2

回答 (1)

天同

2011-02-20 8:45 pm

✔ 最佳答案

What do N1 and N2 represent?

If N1 and N2 are the no. of interference fringes, then the following answer applies:

The equation for a diffration grating is
a.sin(theta) = m入
where a is the grating line spacing
(theta) is the angular position of bright fringes
入 is the wavelength of light used
m is an integer (order of fringes)

The no. of possible fringes is achieved with the max value of sin(theta), which is of value one.

hence, a = m入
i.e. m = a/入
That is, the no. of fringes observed is inversely proportional to the wavelength.
Thus, if N1 > N2, then 入1 < 入2

Conversely, if 入1 > 入2,then N1 < N2

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